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File History says "Reconnect your drive" after KB5124008

Last verified September 2026Tested against Windows 11 24H2 (broken in 26100.9445 and 26100.9457, fixed in 26100.9550), Windows 11 25H2 (broken in 26200.9445 and 26200.9457, fixed in 26200.9550), KB5124008 (8 September 2026) — introduced the failure, KB5129195 (14 September 2026, out-of-band) — cumulative, carries the same failure, KB5124010 (22 September 2026, optional preview) — carries the fix, KB5124006 (22 September 2026, optional preview, 26H1) — carries the fix, October 2026 security update (13 October 2026) — will carry the fix automaticallyWell documented

Microsoft fixed this on 22 September 2026. Install KB5124010 on Windows 11 24H2 and 25H2 — KB5124006 on 26H1 — and File History finds the drive again. The catch is that it is an optional preview update and will not install by itself: go to Settings > Windows Update > Advanced options > Optional updates and choose Download and install, or wait for the 13 October security update, which carries the same fix. If you uninstalled or hid the September updates on earlier advice, unhide them first or KB5124010 will never be offered.

Start here

  1. Confirm this is the September update regression and not a drive problem
  2. Install KB5124010, the optional update that fixes it

The message is misleading in a way that sends people down the wrong path. "Reconnect your drive" reads like a hardware or cabling problem, so that is what most advice online addresses. In this case the drive is fine: the component that draws the File History window crashes before it manages to read its own configuration, and the reconnect prompt is what is left on screen afterwards. For two weeks there was no fix and the only thing that worked was removing the September updates and blocking them. That is no longer true, and it is no longer the right advice — Microsoft shipped the fix on 22 September. What makes it easy to miss is that the fix arrived in an optional preview update that Windows will not install on its own, and that people who blocked the September updates to keep File History alive have blocked the very update that repairs it.

Symptoms

  • File History opens but shows "Reconnect your drive" or asks you to connect a drive, while that drive is connected and usable in File Explorer
  • "Run now" produces the reconnect message instantly and nothing is copied
  • "Turn off" does nothing, and there is no way to pick a different drive
  • Empty File History folders are created on the target drive
  • Reliability Monitor records FileHistory.exe failing with Problem Event Name CLR20r3 and System.InvalidOperationException in module fhuxadapter
  • An InconsistentState entry appears under the File History Configuration folder in your user profile
  • It happens against USB drives, internal drives and NAS network shares alike
  • It began on or immediately after the day KB5124008 installed, or came back the day KB5129195 installed

Why this happens

KB5124008 broke the File History interface, not its drive detection

The recorded crash is a .NET unhandled exception inside fhuxadapter, which is the user-interface layer of File History rather than the component that copies files. That is why the drive checks out by hand while File History insists it is missing, and why repairs aimed at the drive or at Windows system files have nothing to act on. One reporter established the causal link the right way round: after uninstalling KB5124008 on three PCs and seeing File History work again, they reinstalled it on each machine and the failure came back. The out-of-band update of 14 September 2026, KB5129195, is cumulative and carried the same regression, which is why people who had removed KB5124008 found File History failing again as soon as it installed. Microsoft's fix landed on 22 September in KB5124010, and its own support pages for KB5124008 and KB5129195 now carry the acknowledgement and point at that update.

Confirm this is the September update regression and not a drive problem · Install KB5124010, the optional update that fixes it

An older, separate File History problem is easily mistaken for this one

Since the July and August 2026 updates — KB5101684 on Windows 11 25H2 and KB5120249 on Windows 10 22H2 — a different group of people report that File History still copies files to the backup location, but the "Last backup" time never advances and Previous Versions reports that no versions are available. The symptoms overlap enough to confuse the two, but that problem leaves backups running, and KB5124010 does not address it: two reporters who installed KB5124010 say the reconnect failure is gone and files copy again, while the last-copied date still refuses to update. Microsoft has not acknowledged that one, and the release notes for KB5101684 and KB5120249 list no known issues. Telling the two apart is the first thing worth doing, because it decides whether the fix below is relevant to you at all.

Confirm this is the September update regression and not a drive problem

Fixes

Confirm this is the September update regression and not a drive problem

about 10 min

Two different File History failures are circulating and only one of them is fixed by the update below.

Applies to: Windows 11 24H2, Windows 11 25H2, Windows 11 26H1

  1. Check the drive by hand first. Open it in File Explorer, create a file on it and delete it again. If the drive does not appear, or reads and writes fail, stop here — that is a drive problem, not this bug.
  2. Check which update you are on. Press Win+R and run winver. Builds 26100.9445 and 26200.9445 (KB5124008) and 26100.9457 and 26200.9457 (KB5129195) carry the bug; 26100.9550 and 26200.9550 (KB5124010) carry the fix.
    winver
  3. Check the timing. In Settings > Windows Update > Update history, see whether the failure began the day KB5124008 (8 September 2026) or KB5129195 (14 September 2026) installed. That correlation is the strongest signal you have.
  4. Confirm the crash signature if you want certainty. Open Reliability Monitor and look for FileHistory.exe failing with Problem Event Name CLR20r3 and System.InvalidOperationException in module fhuxadapter.
    perfmon /rel
  5. Rule out the older bug. If File History still copies files to the drive and only the "Last backup" time and Previous Versions are wrong, that is the separate July 2026 problem — the update below will not fix it.

Confirmed by the vendor.

Source: Microsoft Q&A, Microsoft Q&A, Microsoft, Microsoft Q&A

Install KB5124010, the optional update that fixes it

about 25 min

This is Microsoft's fix. It exists, but it is a preview update and Windows will not install it for you.

Applies to: Windows 11 24H2, Windows 11 25H2, Windows 11 26H1

  1. Go to Settings > Windows Update > Advanced options > Optional updates.
  2. Find "2026-09 Cumulative Update Preview for Windows 11 (KB5124010)" and choose Download and install. On Windows 11 26H1 the equivalent update is KB5124006.
  3. Restart when prompted, then confirm the build with winver. You want 26100.9550 on 24H2 or 26200.9550 on 25H2.
    winver
  4. Open File History and select Run now. It should find the existing backup on the drive and write a new incremental backup to it rather than showing the reconnect message.
  5. If you would rather not take a preview update, the same fix ships in the 13 October 2026 security update, which installs on its own. Keep copying files by hand until then — see below.
  6. If KB5124010 does not appear under Optional updates at all, you have most likely hidden or paused the September updates. Do the next fix first, then come back here.

Confirmed by the vendor, though some users report it does not help.

Source: Microsoft, Microsoft, Microsoft, Microsoft Q&A, Microsoft Q&A, PCWorld

Unhide the September updates if you blocked them earlier

about 30 min

Blocking KB5124008 and KB5129195 was the only way to keep File History alive for two weeks — and it also blocks the update that repairs it.

Applies to: Windows 11 24H2, Windows 11 25H2

  1. If you hid updates with Microsoft's wushowhide.diagcab troubleshooter, run it again, choose "Show hidden updates", and unhide KB5124008 and KB5129195.
  2. If you paused Windows Update instead, resume it: Settings > Windows Update > Resume updates.
  3. Let the September security updates install and restart. KB5124010 is cumulative, so you are not choosing between File History and September's security fixes — you get both.
  4. Check for updates again, then look under Optional updates for KB5124010. It can take a few minutes to be offered after the security updates land.

Reported to work by 2 users; not confirmed by the vendor.

Source: Microsoft Q&A, Microsoft Q&A, Microsoft

Get a copy of your files off the machine in the meantime

about 30 min

If File History has been showing this message since early September, nothing has been backed up since — and it failed quietly.

Applies to: Windows 11 24H2, Windows 11 25H2, Windows 11 26H1

  1. Copy Documents, Pictures, Desktop and anything else File History was protecting to the backup drive by hand, or to a second drive or cloud storage.
  2. Check how long you have actually been unprotected: open the FileHistory folder on the backup drive and look at the date on the newest file inside it.
  3. Once the fix is installed, open File History, select Run now, and confirm the "Last backup" time actually advances before you rely on it again.

Reported to work by one user; not confirmed by the vendor.

Source: Microsoft Q&A, Microsoft Q&A

Known issues

  • Microsoft fixed this on 22 September 2026 in KB5124010 (builds 26100.9550 and 26200.9550), and in KB5124006 on 26H1. The release note addresses File History failing to back up or restore to an external drive or network location while incorrectly showing "Reconnect your drive". Both are optional non-security preview updates offered under Optional updates, so they do not install automatically; the fix reaches everyone else in the 13 October 2026 security update.

    Affects Windows 11 24H2, Windows 11 25H2, Windows 11 26H1 · Status: fixed

  • Microsoft acknowledged the bug on the KB support pages rather than on the Windows release health known-issues pages. The known-issues sections of KB5124008 and KB5129195 now both carry a File History entry resolved "in Windows updates released on and after September 22, 2026". Neither entry was there on 16 September. As of 25 September 2026 the 24H2, 25H2 and 26H1 release-health pages still do not list File History at all.

    Affects Windows 11 24H2, Windows 11 25H2, Windows 11 26H1 · Status: fixed

  • A minority report the fix did not take. One reporter on 23 September 2026 says that after KB5124010 File History can be turned on again but "does nothing" when Run now is clicked. Against six people reporting it restored, this looks like a smaller separate fault rather than the fix failing, but it is not resolved and Microsoft has not commented on it.

    Affects Windows 11 25H2 · Status: open

  • The older, separate File History problem is untouched by this fix and remains unacknowledged. Since KB5101684 (Windows 11 25H2) and KB5120249 (Windows 10 22H2) in July 2026, backups still run but the last-copied date does not advance and Previous Versions reports nothing available. Two reporters confirmed on 25 September that KB5124010 restored backups while leaving that symptom in place.

    Affects Windows 11 25H2, Windows 10 22H2 · Status: open

If none of this worked

Two other things break File History and are not this bug. If File History still copies files to the drive but the "Last backup" time never advances and Previous Versions shows nothing, that is the separate problem reported since the July 2026 updates — KB5101684 on Windows 11 25H2 and KB5120249 on Windows 10 22H2 — and KB5124010 does not fix it. If File History stopped working before 8 September 2026, or the drive genuinely does not appear in File Explorer, start with the drive, its cable and its power instead. SFC, DISM, restarting the File History service and deleting the File History configuration folder are all reported in these threads as tried and unsuccessful against this failure, so they are not worth your time here.

Common questions

How do I get KB5124010? It is not installing.
It will not install on its own — it is an optional non-security preview update. Go to Settings > Windows Update > Advanced options > Optional updates, find "2026-09 Cumulative Update Preview for Windows 11 (KB5124010)" and choose Download and install. On Windows 11 26H1 the equivalent is KB5124006. If it is not listed, the usual reason is that you hid or paused the September updates to keep File History working — unhide them first. If you would rather not run a preview build, the same fix is included in the 13 October 2026 security update, which does install automatically.
Does the 14 September out-of-band update (KB5129195) fix this?
No. Microsoft's list of what KB5129195 fixes covers CVE-2026-62721, Remote Desktop Services, Plan9 host folder shares in Hyper-V Linux VMs and multichannel USB audio — File History is not among them. Reporters installed it on 14 and 15 September and said the failure was unchanged, and because it is cumulative it re-broke File History for people who had uninstalled KB5124008. KB5129195's own support page now acknowledges this and points at KB5124010 as the fix.
Should I still uninstall the September security update?
No — not any more. That was the only option before 22 September, and it meant giving up that month's security fixes, including the patch for CVE-2026-62721 in KB5129195. Now that KB5124010 exists there is no trade-off left to make: it is cumulative, so it carries September's security fixes and the File History repair together. If you already uninstalled and hid those updates, unhide them and take KB5124010.
Is my backup drive failing?
Very unlikely if it reads and writes normally in File Explorer. Reporters verified their drives by hand and with Microsoft support, and one saw the identical failure against a NAS over the network. The "Reconnect your drive" text comes from a component that crashed before it could read its own configuration — it is not a statement about the drive.
Will SFC or DISM fix this?
No, and they were tried extensively before the fix existed — in one case by a Microsoft support technician connected remotely, and by one reporter who reinstalled Windows from scratch only to hit the failure again after updating. The crash sits in a .NET component of the File History interface rather than in Windows system file integrity, so a system file repair has nothing to act on.
I installed KB5124010 and File History still will not run. Now what?
Check which symptom you have left. If backups now copy but the "Last backup" time does not advance and Previous Versions is empty, you have the separate July 2026 problem, which KB5124010 does not address and Microsoft has not acknowledged — two reporters confirmed exactly that on 25 September. If File History turns on but Run now does nothing at all, one reporter is in the same position as you and there is no known fix; back up by hand and report it through Feedback Hub. Either way, do not uninstall the September updates expecting it to help.
Does this affect Windows 10 as well?
There are reports of broken File History on Windows 10 in the same period, but they name different updates and we have not confirmed the same crash signature there. Treat this page as being about the Windows 11 KB5124008 failure specifically.

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Related problems

Sources

  • September 22, 2026—KB5124010 (OS Builds 26200.9550 and 26100.9550) PreviewOfficial

    Microsoft · Support page · checked Sep 25, 2026

    • KB5124010 was released on 22 September 2026 and produces OS builds 26100.9550 and 26200.9550.
    • It states: "This update addresses an issue where File History might fail to back up or restore files to an external drive or network location. Affected devices might incorrectly display a 'Reconnect your drive' message even when a compatible backup drive is connected and working properly."
    • KB5124010 is a non-security preview update, offered under Optional updates rather than installed automatically.
    • Its own known-issues section lists the Credential Guard domain trust problem and the USB Audio Class 1.0 problem, and no longer lists File History.
  • September 8, 2026—KB5124008 (OS Builds 26200.9445 and 26100.9445)Official

    Microsoft · Support page · checked Sep 25, 2026

    • KB5124008 was released on 8 September 2026 and produces OS builds 26100.9445 and 26200.9445.
    • Its known-issues section now includes a File History entry: users are unable to create or update backups and the device incorrectly displays "Reconnect your drive" despite a connected drive.
    • That entry states the issue is "Resolved in Windows updates released on and after September 22, 2026 such as KB5124010."
    • The File History entry was not present on this page when it was checked on 16 September 2026.
  • September 14, 2026—KB5129195 (OS Builds 26200.9457 and 26100.9457) Out-of-bandOfficial

    Microsoft · Support page · checked Sep 25, 2026

    • KB5129195 was released on 14 September 2026 as an out-of-band update producing OS builds 26100.9457 and 26200.9457.
    • Its improvements cover CVE-2026-62721, Remote Desktop Services instability, Plan9 host folder shares in Hyper-V Linux VMs, and multichannel USB Audio Class 1.0 — not File History.
    • Its known-issues section now carries a File History entry noting the problem was fixed in updates released on or after 22 September 2026.
  • Windows 11's File History bug is fixed, but it won't install on its ownReputable

    PCWorld · News · checked Sep 25, 2026

    • Reported 23 September 2026 by Mikael Markander: "Both updates are optional Windows 11 updates that you must install manually."
    • It directs readers to Windows Settings > Windows Update > Advanced options > Optional updates to get the fix.
    • It states that otherwise "the fix will roll out as part of October's Patch Tuesday."
  • File History problems after installing KB5124008, KB5126052, and KB890830Community report

    Microsoft Q&A · Forum · checked Sep 25, 2026

    • Around eight to ten distinct people in this thread report File History failing with a reconnect-drive message after the September 2026 updates.
    • The original reporter, BobH3027, established cause both ways round: uninstalling KB5124008 restored File History on all three affected PCs, and reinstalling it reproduced the failure (post dated 9 September 2026).
    • SFC and DISM were tried without success; one reporter reinstalled Windows from scratch and hit the failure again only after installing updates.
    • FileHistory.exe crashes are recorded with Problem Event Name CLR20r3 and System.InvalidOperationException in module fhuxadapter.
    • Mike_A_P (14 September) and MollFran88 (15 September) both confirm the out-of-band update KB5129195 did not fix File History.
    • On 23 September 2026 Ezio De Pazzi reports "installed the latest updates on Sep. 23rd, and file history back online" and MollFran88 replies "Agreed, all good now."
  • File History stopped working after a recent updateCommunity report

    Microsoft Q&A · Forum · checked Sep 25, 2026

    • Around six distinct people report File History failing after KB5124008, KB5126052 and KB5129195 (build 26200.9457).
    • Mike_A_P, 22 September 2026: "Confirmed, working here after KB5124010 (26200.9550). File History reconnected to existing backup on external drive, has written a new incremental backup, and restore also checked and functioning."
    • Peter LaBounty, 23 September 2026: "File History started working for me again, after Update KB5124010."
    • Carolyn Kay, 23 September 2026, on installing KB5124010: "I had to force the update, but it worked."
    • Fahrizal, 23 September 2026, reports the fix did not work for him: "still broken on mine. it can be turned ON now. but it does nothing when i click RUN NOW."
    • Reporters had previously tried restarting the fhsvc service, deleting the File History configuration, reselecting the drive, uninstalling KB5124008 and pausing Windows Update.
  • File History. Reconnect Your DriveCommunity report

    Microsoft Q&A · Forum · checked Sep 25, 2026

    • Three distinct reporters; the original poster's File History failed against a NAS target, showing empty backup folders and a reconnect message.
    • Uninstalling KB5124008 restored File History on one laptop, while on an identical second laptop the update was absent from Uninstall updates and wusa /uninstall /KB:5124008 returned an error.
    • On 15 September 2026 two reporters state KB5129195 (build 26200.9457) broke File History again after it had been working.
    • The thread documents hiding KB5124008 and KB5129195 with Microsoft's wushowhide.diagcab troubleshooter to stop Windows reinstalling them.
    • On 22 September 2026 volunteer moderator Ramesh posted that KB5124010 (builds 26200.9550 and 26100.9550) resolves the File History error, quoting the release note.
  • File History problems after installing KB5124008, KB5126052, KB5126146, KB5122878, and KB890830Community report

    Microsoft Tech Community · Forum · checked Sep 25, 2026

    • Roughly ten to twelve distinct people report the same File History failure after the September 2026 updates; some names plausibly overlap with the Microsoft Q&A threads and were not double-counted.
    • An InconsistentState entry appears under C:\Users\<user>\AppData\Local\Microsoft\Windows\FileHistory\Configuration on an affected PC.
    • In the thread's latest reply, dated 25 September 2026, the original poster reports that after KB5124010 File History can find and run backup drives and all new files are copied, but the last copy date of the files is still not updated.
  • The KB5124010 file history update still seems a bit off. The problem with KB5101684 is still there.Community report

    Microsoft Q&A · Forum · checked Sep 25, 2026

    • One reporter, on Windows 11 25H2 build 26200.9550, states KB5124010 fixed the KB5124008 problem and file backups now work normally.
    • The same reporter states a separate File History problem persists after KB5124010: clicking Run now does not advance the last-copied date, version history does not update, and Previous Versions reports no versions available.
    • The reporter attributes that separate problem to KB5101684 and KB5120249 from July 2026, not to the September updates.
  • Windows 10/11 File History Appears to Be Broken After Recent UpdatesCommunity report

    Microsoft Q&A · Forum · checked Sep 25, 2026

    • A separate File History problem is reported from late July and August 2026, after KB5101684 on Windows 11 25H2 and KB5120249 on Windows 10 22H2.
    • In that problem File History still writes files to the backup location, but the "Last backup" time does not advance and Previous Versions reports that no versions are available.
    • Re-checked 25 September 2026: the thread is unchanged with its latest reply dated 17 August 2026, and the release notes for KB5101684 and KB5120249 list no known issues, so Microsoft has not acknowledged it.