What to check when a Microsoft 365 app closes or stops responding?
Determine whether the failure affects one application, one file, one user or the entire device. Add-ins, updates, profiles, printers, corrupted files, antivirus software and the Office installation can all be involved. Testing another file and starting the application in safe mode helps isolate the cause before repair or reinstallation.
Risks to review
- Force repeated shutdowns and lose unsaved changes.
- Delete profiles, PST, templates or plugins without backup.
- Reinstall Office before confirming account, license and local data.
- Permanently disable security to test a hypothesis.
Safe recommendations
- Record the application, file, action and exact time of failure.
- Test another file and start the application in safe mode to isolate add-ins.
- Protect local documents, PST files, templates and required settings.
- Install official Windows and Microsoft 365 updates.
- Use Office Repair before performing a full reinstall.
- Check logs and disk health if multiple applications crash.
When to seek specialized help
- Outlook contains critical PST files or add-ins.
- The bug affects several users or appeared after an update.
- There are disk errors, corrupted files, or loss of information.
Reference sources
These public sources provide general good-practice guidance. They do not replace an assessment of your environment.