How to fix fail authentication

Follow these steps to troubleshoot phone-based authentication for Microsoft Teams:

1. Confirm the issue
   • Make sure the sign-in problem is specifically with the phone/SMS or call verification step when signing in to Teams.
   • If the error says authentication or verification did not complete, continue with the steps below.
2. Check Microsoft Authenticator (if used)
   • Ensure the Microsoft Authenticator app is unlocked on the device.
   • Turn on notifications for Microsoft Authenticator and verify they are not set to silent.
   • Install the latest version of Microsoft Authenticator from the store.
   • Make sure the device has a stable internet connection (try switching between Wi‑Fi and mobile data).
   • Verify the device’s date and time are set correctly (automatic time is recommended).
3. Check SMS/phone verification issues
   • If not receiving verification codes:
     • Avoid making excessive or repetitive requests for codes; this can cause temporary blocking.
     • Confirm the phone does not block texts from unknown numbers.
     • Ensure the phone’s SMS inbox is not full and the messaging app is working correctly.
     • Do not use a VOIP number; use a mobile phone number instead.
   • If using voice call verification:
     • Ensure the phone is turned on and has service.
     • If prompted during a call, respond correctly (for example, press the pound key # when instructed).
4. Verify security info (work or school account)
   • Sign in to the Security info page for the work or school account.
   • Check that the phone number is entered correctly (country/region code and number).
   • If needed, choose Update info and add or correct the mobile phone number.
5. If codes or calls still do not arrive
   • There may be temporary blocks or delays due to unusual activity or heavy traffic from the region. These usually resolve automatically after some time.
   • Try an alternate verification method if available (Microsoft Authenticator app, verification code, or another phone number).
6. If sign-in to Teams still fails
   • For an organization (work or school) account, contact the IT admin or sysadmin. There may be an issue with the domain or Office 365 account configuration, or the admin may need to reset or reconfigure MFA methods.
   • If the phone number has been flagged or blocked for verification at the service level, a support ticket with Microsoft (often via the tenant’s admin/Data Protection support) may be required to reset MFA or clear the block.

References:

• Why am I having trouble signing in to Microsoft Teams?
• Troubleshoot problems with Microsoft Authenticator
• Authentication methods in Microsoft Entra ID - Voice call
• Common problems with two-step verification for a work or school account
• "Account verification system is having trouble" error message when you try to sign in by using a work or school account
• 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• I need to reset my mfa methods - Microsoft Q&A
• Can't add telephone number to my Microsoft 365 account - Microsoft Q&A
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A
• Authentication did not complete