Microsoft smart app control blocks my Word, Excel and Powerpoint. Microsoft 365 and Office | Word | For home | Windows

Run a full Online Repair of Microsoft 365 first, because the displayed Excel message is an Office application error and does not show a Smart App Control block notification.

Repair Microsoft 365

1. Close Word, Excel, PowerPoint, and any other Office applications.
2. Right-click Start and select Installed apps.
3. Find Microsoft 365 or Microsoft Office.
4. Select the three dots beside it, then Modify.
5. If prompted for permission, select Yes.
6. For a Click-to-Run installation, select Online Repair → Repair.
   • Choose Online Repair, not Quick Repair, because it performs the more complete repair.
   • If the installer instead shows an MSI repair window, select Repair → Continue.
7. Complete the repair, restart Windows, and test Excel, Word, and PowerPoint.

This repairs the entire Office suite even when the error appears in only one application.^1^

Only change Smart App Control if Windows explicitly identifies it

A genuine Smart App Control block normally appears as a Windows Security notification saying that an app is untrusted or blocked. The screenshot contains no such notification.

If a separate Windows Security notification explicitly names an Office executable:

1. Install all available updates from Settings → Windows Update → Check for updates, including current Microsoft Defender updates.
2. Restart and test Office again.
3. If Office is still explicitly blocked, open Windows Security → App & browser control → Smart App Control settings and review its status.

Smart App Control does not provide a per-application allow list. The only available bypass is to turn Smart App Control off, which reduces protection for the entire device—not just Office.^2^

Avoid disabling it unless the Windows notification specifically confirms that it is blocking the installed Microsoft Office applications. Recent Windows updates permit Smart App Control to be re-enabled from Windows Security on supported devices, but update Windows before changing the setting.^2^

If Online Repair completes but all three applications still show the same error, record the exact Microsoft 365 product listed under Installed apps, the Windows version shown by winver, and whether any separate Windows Security block notification appears. Those details distinguish an Office installation failure from an actual security-policy block.

References

1. Windows 11
2. Smart App Control Frequently Asked Questions | Microsoft Support