stuck at error code 399287

Question

Stuck at error code 399287. sms verification code not working. Request you to do the needful.

Answer 1

Hi @Magnum Hospitality, 

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

Regarding the issue where you are receiving error code 399287 and are unable to receive or use the SMS verification code to sign in, I’d like to ask a few questions to better understand your situation and assist you more effectively.

 I’d like to ask a quick questions to better understand your situation and assist you effectively:       

Could you please clarify whether you are an end user or an admin?              

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:                  

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

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          

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.         

Please note that forum moderators have no control over user accounts, especially when it comes to logging in to your account, resetting your password, changing your access, etc.                       

Thank you again for your time and understanding. I really appreciate your patience, and I’m here to help. Looking forward to your response!                       

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Answer 2

Error code 399287 indicates that the phone number used for SMS verification has been blocked for Azure/Microsoft Entra ID MFA due to a “bad reputation” or similar protection trigger on Microsoft’s side. This is not something that can be fixed from the portal or by changing local settings.

Self-service steps are limited here. If other verification methods (such as Microsoft Authenticator, alternate phone, or email) are available on the account, use one of those to sign in and then add a new, clean phone number as an MFA method.

If SMS is the only available MFA method or all SMS attempts fail with 399287, the issue must be handled by Microsoft support/data protection:

1. For a work/school (Entra ID) account where access is blocked and no other MFA method works, open a support case from an existing admin account in the tenant (if available) or via your organization’s Microsoft 365/Azure support channel.
2. If this is the only admin account and it is locked, the Microsoft Data Protection team must reset MFA and clear the block after verifying identity. This requires opening a support request via Microsoft support (frontline support will route to the Data Protection team).
3. Clearly state in the ticket that:
   • SMS MFA fails with error 399287.
   • The phone number appears to have a bad reputation and is blocked for verification.
   • MFA reset and removal of the reputation block are required.

There is no documented self-service way to remove the “bad reputation” flag or unblock the number; it requires Microsoft support intervention.

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References:

• "We didn't receive a response" error message when you try to sign in by using Azure Multi-Factor Authentication
• 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - 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