Microsoft Authenticator

Hi @Kingston Tosi,        

Thank you for posting your question in the Microsoft Q&A forum.                

Regarding that you can't log in to your account due to Microsoft Authenticator.        

If you are an end user I would recommend you contact your account's Admin to reset your MFA settings through the Microsoft Entra Admin Center. Ask your administrator to follow these steps:    

1. Sign in to Microsoft Entra admin center with the admin account 
2. Go to Users 
3. Select the affected user account 
4. Open Authentication methods 
5. Revoke sessions 
6. Select Require re‑register MFA 
7. Save the changes               

Revoke MFA sessions and require re-register in the Microsoft Entra admin center  

Please note that forum moderators don’t have access to user accounts and cannot assist with actions such as password resets, login changes, or account recovery.  

You could provide your admin this article for a better view: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID |…               

If you’re unsure who the Global Admin is within your organization, you can find guidance on locating them here: How do I find my Microsoft 365 admin? - Microsoft Support.                  

Thank you again for your time and understanding. While my initial response may not resolve the issue immediately, I’d like to gather more details about your situation so I can assist you more effectively.               

I really appreciate your patience, and I’m here to help. Looking forward to your response!                       

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Because the phone changed, the old Microsoft Authenticator registration is still tied to the previous device, so the new phone is not receiving prompts or codes. Authenticator on a new phone cannot approve sign-ins until the account’s MFA registration is reset or another verification method is used.

Use these steps depending on what is available:

1. Try another verification method (if configured)

• If the sign-in screen offers options like Text, Call, or Email code, choose one of those instead of Authenticator.
• If codes are not arriving, follow the guidance for missing verification codes:
  • Avoid repeatedly requesting codes; too many requests can cause a temporary block.
  • Check if the phone is blocking texts from unknown numbers.
  • Confirm the phone number and email are correct in the account’s Security info page when access is available.
  • Do not use a VOIP number; use a mobile number instead.

2. If no alternative method works Because this is a school (work/school) account and the new phone’s Authenticator is not registered, the school’s IT/Help desk or Microsoft 365 admin must reset the MFA settings for the account:

• Contact the school’s IT support or help desk.
• Ask them to reset or clear the account’s multi-factor authentication / authentication methods in Microsoft Entra so that re-registration is required.
• After they reset MFA, sign in again; the sign-in process will prompt to set up Microsoft Authenticator on the new phone (usually by scanning a QR code).

3. If the device was lost or replaced

• Inform the school’s Help desk that the old phone was replaced.
• They can clear the old device registration so that the new phone can be enrolled.

Until the admin resets MFA or another working method is available, the new Authenticator app cannot complete sign-in for the school account.

References:

• Common problems with two-step verification for a work or school account
• Troubleshoot problems with Microsoft Authenticator
• How to add your accounts to Microsoft Authenticator
• Microsoft authenticator sending me into a spiral - Microsoft Q&A
• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A
• Microsoft Authenticator app doesn't show 6-digit OTP code - Microsoft Q&A
• Requesting a Tenant Admin MFA Reset - Microsoft Q&A
• Having problems getting text codes to confirm my account - Microsoft Q&A