MFA & Verification Issues

How to Fix Microsoft Authenticator Error 500121 (MFA Unavailable)

Algirdas Jasaitis Oct 16, 2026 868 views

Question details

The user is unable to sign into their Microsoft 365 work or school administrator account due to Microsoft Authenticator Error 500121, as MFA approval notifications are not being received.

How to Fix Microsoft Authenticator Error 500121 When MFA is Unavailable

Product: Microsoft Authenticator / Microsoft 365
Device & OS: not provided
Scenario: Attempting to sign into a Microsoft 365 work or school administrator account with Two-Step Verification enabled.
Observed behavior: The sign-in process fails with Error 500121 because the Authenticator app does not prompt for approval, effectively locking the administrator out of the security management dashboard.

Before you start

Ensure you have access to any alternative verification methods you may have previously set up, and avoid posting your account email address or passwords in public support forums.

Solution 1Recommended

Contact Another Administrator or Microsoft Support

Since you are locked out of your admin account, you cannot reset your own MFA settings. You must escalate this to another admin or Microsoft Support to regain access.

Work and school accounts are managed at the organizational level. When an administrator is locked out by an MFA failure, a secondary administrator must intervene. If you are the sole administrator, only Microsoft's Data Protection team can assist.

Reach out to a secondary administrator

Contact another global administrator within your organization's Microsoft 365 tenant.

Reset MFA settings via Entra ID

Ask the active administrator to access the Microsoft Entra ID (formerly Azure Active Directory) admin center, navigate to your user profile, and select 'Authentication methods'.

Require re-registration

Have the administrator choose 'Require re-register MFA' or delete the existing Microsoft Authenticator entry linked to your account.

Contact Microsoft Data Protection

If you are the only administrator on the tenant, contact Microsoft Support directly via phone. Ask for the Data Protection team to verify your identity and regain tenant access.

Contact Another Administrator or Microsoft Support

Temporary Access Pass: An active administrator can also issue a Temporary Access Pass (TAP) for your account, allowing you to bypass MFA temporarily and log in to fix your Authenticator settings.

Solution 2

Temporarily Disable Two-Step Verification (Personal Accounts)

If this error occurs on a personal Microsoft account and you still have an alternative sign-in method, you can manage your security settings online to bypass the app.

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Frequently Asked Questions

Why am I getting Microsoft Authenticator Error 500121?

Error 500121 occurs when authentication fails during a multi-factor authentication (MFA) request. This usually happens if the Authenticator app doesn't receive the push notification, if the authentication token has expired, or if the user repeatedly denies the approval prompt.

Can I reset my MFA if I am the only administrator on the tenant?

If you are the sole global administrator for a Microsoft 365 work or school account and get locked out by an MFA error, you cannot reset your own MFA online. You must contact the Microsoft Data Protection team via phone support to verify your business identity and have them reset the account access.

Why is my one-time password 8 digits but the login prompt asks for 6 digits?

This mismatch usually occurs when you are looking at a different token type within the Authenticator app (such as an Azure AD token versus a personal Microsoft account token) or using a third-party app incorrectly. Ensure you are tapping the specific account you are trying to sign into to get the correctly formatted time-based code.

Login & Account Issues