How to fix Authenticator app

Try these steps in order:

1. Make sure Microsoft Authenticator is unlocked on the phone. If the app is locked, the sign-in prompt or number entry box may not appear.
2. Check that notifications are enabled for Authenticator. Silent or disabled notifications can prevent the approval prompt from showing.
3. Make sure the phone has a working internet connection. Switch between Wi‑Fi and mobile data, and make sure Airplane mode is off.
4. Update Microsoft Authenticator to the latest version. Versions older than 12 months are not supported.
5. In Authenticator, open Settings and turn off battery optimization if that option is available.
6. Check the phone’s Date & time settings and make sure they are correct.
7. If a VPN is enabled, disconnect it and try again.
8. If the prompt was expected on the current phone but never appeared, check whether it was sent to an older device where Authenticator was last used. If the old device is still available, approve the sign-in there.
9. If the old device is no longer available, use a different verification method such as SMS, if that option is offered.
10. If the message says “Authenticator did not complete login” and the sign-in still cannot be completed, finish the login inside Authenticator, Company Portal, or the primary Microsoft app on the device.
11. If none of the above works and this is a work or school account, contact the IT admin to reset MFA or allow re-registration.

References:

• Troubleshoot problems with Microsoft Authenticator
• Microsoft Authenticator FAQs
• Authenticator Did Not Complete Login
• Authentication did not complete
• My old phone has broken so I can’t access the old authenticator app so now I can’t log in on the phone as I need the old phone to login which I broken - Microsoft Q&A