Smart App Control is blocking a game, launcher or mod

Every decision after this depends on whether the blocked file is something you trust. Guessing is how people end up disabling a security feature over a file they would not have run anyway.

Applies to: Windows 11 build 22572 and later

1. If the pop-up is still on screen, select Learn more. It names the driver or file that was blocked.
2. If it has gone, open Windows Security > Virus & threat protection > Protection history and search the entries for Smart App Control or Blocked app.
3. Look at where the blocked file came from. A file inside a game you installed from Steam or the publisher's own installer is a different proposition from one that arrived with a mod pack from a file host.
4. If you do not recognise it, stop. A block on something you cannot account for is the feature doing its job, and the answer is not to switch the feature off.

Confirmed by the vendor.

Source: Microsoft

Evaluation mode does not block anything, so if you are in it, this is not your problem at all.

Applies to: Windows 11 build 22572 and later

1. Open Windows Security > App & browser control and find the Smart App Control section. If there is no such section, the feature is not on this device and you can stop here.
2. On means enforcement mode — it is actively blocking. Evaluation means it is observing without blocking. Off means it is not running.
3. If it says Evaluation and something is still being blocked, the block came from somewhere else: Microsoft Defender, SmartScreen, memory integrity, or the game's own anti-cheat. Check Protection history to see which.
4. Note whether this machine was recently reset or clean installed. Smart App Control starts in evaluation mode after a clean install and may have switched itself to enforcement since.

Confirmed by the vendor.

Source: Microsoft

A properly signed file is allowed through even when Microsoft's prediction service has no opinion on it. This solves the problem without weakening anything.

Applies to: Windows 11 build 22572 and later

1. Re-download the tool from the developer's own site or repository rather than a mirror or aggregator. Repackaged copies lose the original signature.
2. Check for a newer release. Projects that get caught by this often ship a signed build afterwards precisely because of the complaints.
3. For peripheral and RGB utilities, install the manufacturer's current package rather than an old one you already had — the old driver inside it is usually what triggers the block.
4. If the project has no signed build, report it to them. There is nothing you can configure on your side that makes an unsigned binary acceptable to this feature.

Confirmed by the vendor.

Source: Microsoft

Microsoft itself suggests this for installers that use files which cannot be signed. It is also the step you may not be able to reverse, so treat it accordingly.

Applies to: Windows 11 build 22572 and later

1. Confirm first that you trust the specific file you identified earlier, and that you got it from its real source.
2. Open Windows Security > App & browser control > Smart App Control and set it to Off.
3. Do what you needed to do — complete the install, or run the tool.
4. Go straight back to the same screen and see whether the option to turn it on again is available to you. That is the only reliable way to find out which of Microsoft's two statements applies to your machine.
5. If it cannot be re-enabled and you want it back, the documented route is a clean install or Reset this PC — Microsoft says a reset counts as a clean install. Keep my files preserves your documents but removes installed apps.

Confirmed by the vendor.

Source: Microsoft, Microsoft