Global Admin Locked Out – Error 399287 – MFA Reset Required –

Question

Dear Microsoft Support / Data Protection Team,

I am writing to request urgent assistance. I am the sole Global Administrator of my Microsoft 365 tenant and I am completely locked out due to MFA failure.

--- ERROR DETAILS ---

Error Code: 399287

--- SITUATION ---

I cannot complete MFA because:

1. Microsoft Authenticator is unavailable / not configured on my current device.
2. SMS verification fails immediately with error 399287 — no code is sent. This indicates the phone number has been flagged by Microsoft's PhoneReputation service.
3. There are no other Global Administrators in the tenant who could reset my MFA.
4. mysecurityinfo (aka.ms/mysecurityinfo) also requires MFA to access, so I cannot add alternative methods.

--- REQUEST ---

I am requesting escalation to the Data Protection / Tenant Recovery team to:

1. Reset / clear my MFA methods so I can re-register from scratch?
2. Remove the bad-reputation flag from phone number?.

Thank you for your urgent attention to this matter.

Answer 1

Hello Karol Frutos,

We need few details to proceed further. Please check your Private messages tab and provide those details.