Lost access to authenticator MS365 Admin - can't use phone number as MFA - error 399287

Question

Lost access to authenticator MS365 Admin - can't use phone number as MFA - error 399287

GVDM 0

I lost access to my admin account and can't use the phone number as a verification method (error 399287 comes up).

Admin account: [Moderator note: Personally Identifiable Information removed]@madprocessorvof.onmicrosoft.com

I am the only administrator. I do not have access to Microsoft authenticator anymore so I would like to use this method (text or call) to verify my identity.

GVDM 0 Reputation points

2026-10-05T14:29:24.4766667+00:00

I strongly believe the problem is the same as described in this article: https://www.linkedin.com/pulse/sms-authentication-error-399287-microsoft-365-log-in-evgenij-danilov-pg31e

1 answer

Your answer

GVDM 0 Reputation points

2026-10-05T14:29:24.4766667+00:00

I strongly believe the problem is the same as described in this article: https://www.linkedin.com/pulse/sms-authentication-error-399287-microsoft-365-log-in-evgenij-danilov-pg31e

Answer 1

Dear @GVDM

I understand that you are the only administrator for the Microsoft 365 tenant, you no longer have access to Microsoft Authenticator, and SMS/phone verification fails with Error 399287.

If there is no other Global Administrator who can reset your authentication methods, there is no self-service way to reset MFA from the tenant. Error 399287 can occur when phone-based verification is blocked by Microsoft’s security/risk controls, so repeatedly trying SMS or voice verification is unlikely to resolve the issue.

In this situation, I recommend contacting Microsoft Support and requesting a tenant administrator recovery / MFA recovery case.

I recommend contacting Microsoft Support by phone and explicitly requesting that a support case be opened and escalated to the Data Protection / Tenant Recovery team.

From what I know, you will need to get past the initial AI system to reach the live support team. You can refer to the guide below for tips on how to get through more easily: User's image If you have tried phone support and it's not working, please follow this link to create a trial tenant after that you will be able to access to Microsoft 365 Admin Center to raise the ticket

Assuming that you have already created an account after registering a free trial and you can go to Microsoft 365 admin center and click "Help & support" icon to raise your ticket.

User's image

Please mention that you are raising ticket on behalf of the affected tenant that you do not have access to.

On the other hand, if you do create the trial and it resolves the issue, please remember to cancel the subscription afterward to avoid any related charges.