Can't to access mfa

Question

Error Code: 500121

Request Id: [Moderator note: Personally Identifiable Information removed]

Correlation Id: [Moderator note: Personally Identifiable Information removed]

Timestamp: 2026-08-06T03:04:17Z

Answer 1

Hi,

The AADSTS500121 error generally indicates that the required multi-factor authentication (MFA) challenge could not be completed, so the sign-in request was blocked.

To better understand your situation, could you please clarify the following?

• Did this issue start after changing your phone or reinstalling the Microsoft Authenticator app?
• Are you unable to receive the MFA notification or verification code, or does the authentication fail after you approve the request?
• Are you the Microsoft 365 administrator for your organization, or is this a standard user account?

If you're a standard user, I'd recommend contacting your Microsoft 365 administrator. They can review your MFA configuration and, if necessary, reset or require re-registration of your authentication methods.

If you're the administrator, please let me know whether there are any other Global Administrators in your tenant who can access the Microsoft Entra admin center. That will help determine the most appropriate recovery option.