Locked out as sole Global Admin — MFA Error 399287, phone reputation block

Question

Hello Microsoft Q&A team,

I am the sole Global Administrator of my Microsoft 365 tenant and I am completely locked out due to MFA Error 399287 (phone reputation block on my registered SMS number). I have no other working MFA method available — the Microsoft Authenticator app is not installed on any device, and I cannot install/register it because I cannot complete sign-in. SMS to my registered number now fails immediately with error 399287, which based on prior threads in this forum indicates a backend block by Microsoft's PhoneReputation service.

I am requesting escalation to the Microsoft Data Protection team / Engineering (PG) team to:

1. Remove the phone reputation block on my registered number, OR
2. Reset the MFA configuration on my account so I can register a new method.

--- Technical details ---

Error Code: 399287

Request Id: 00e65156-f9ea-4613-8b63-61a9eb982b00

Correlation Id: 4f1fade8-<removed PII>

Timestamp: 2026-04-28T19:24:14Z

Answer 1

Hello Rocco Wammes,

Thank you for sharing your details (user's email address, tenant id, phone number, country code and country) with us over Private Message

I have reached out to the engineering team to unblock MFA for your account. They have now unblocked it from the backend and removed the bad reputation on it. You should be able to log in to the Azure Portal without any issues.

Please try logging in and check if you can complete SMS authentication without any errors. Let me know if you encounter any issues.

I hope this information is helpful. Please feel free to reach out if you have any further questions.

If this answers your query, do click and Yes for was this answer helpful, which may help members with similar questions. If you have any other questions, let me know in the “comments” and I would be happy to help you.