My Authenticator app keeps notifying me that someone signed into my account on Microsoft but when I go in to check the notifications it’s gone.

Those notifications indicate sign-in activity that must be reviewed and secured from the account security pages rather than inside Authenticator alone.

Take these steps:

1. Review recent sign-ins and unusual activity
   1. Go to the Security basics page and sign in.
   2. Select Review activity to open the Recent activity page.
   3. Check both Unusual activity and Recent activity sections for sign-ins that are not recognized.
   4. For any event that is not yours:
      • If it appears under Unusual activity, expand it and select This wasn't me.
      • If it appears under Recent activity, expand it and select Secure your account.
2. Change the password and update security info
   1. From Security basics, select Change password and set a strong new password.
   2. On the Security settings page, review phone numbers, email addresses, and devices; remove anything unfamiliar and consider removing all trusted devices.
3. Handle unrequested prompts
   • For any “Are you trying to sign in?” prompt that was not initiated, always select Deny.
   • Then go to your recent activity and, for any event you don’t recognize, select Secure your account.
4. Strengthen protection
   • Turn on two-step verification / multi-factor authentication if not already enabled.
   • Keep the device list up to date in account security settings and remove old devices so notifications do not go to devices that are no longer controlled.

If sign-ins continue to appear that are not yours even after changing the password and securing the account, continue to deny all prompts and regularly review Recent activity to ensure no unauthorized access is successful.

References:

• What happens if there's an unusual sign-in to your account
• Check the recent sign-in activity for your Microsoft account
• Using Outlook mobile to sign in
• View your work or school account sign-in activity from My Sign-ins
• Microsoft Authenticator FAQs
• Troubleshoot problems with Microsoft Authenticator
• Sign in using Microsoft Authenticator