Fix Sign-in Error Code AADSTS500121
Authentication failed during strong authentication request
Error Message
We didn’t hear from you. We sent an identity verification request to your Microsoft Authenticator app, but we didn’t hear from you in time.
Root Cause Analysis
This error can occur for several reasons, such as:
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The user did not complete the MFA prompt.
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The user accidentally selected “No, it’s not me” during verification.
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The session timed out while the user was multitasking.
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Issues with the user’s authentication setup, such as configuration errors, outdated versions, or connectivity problems.
Error Examination
When a user’s sign-in is blocked due to an MFA failure, admins can analyze the failure causes using Microsoft 365 sign-in activity reports.
License Requirement
Microsoft Entra ID P1 license
Role Requirement
Report Reader
How to Find Strong Auth Failed Error 500121 Details in Microsoft 365 Sign-in Logs?
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Sign in to the Microsoft Entra admin center.
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Go to the Entra ID » Monitoring & health » Sign-in logs.
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Apply the following filters to find and analyze Microsoft 365 sign-ins that were blocked because of MFA failures.
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Sign-in error code: 500121
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Username: Enter the affected user’s UPN.
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Date: By default, this filter is set to show sign-in activity for the past 24 hours, but you can customize the date range to include up to 7 or 30 days.
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You can further narrow your search using additional filters, such as correlation ID, request ID, and other user-specific details in Microsoft Entra ID.
How to Fix Authentication Error Code 500121 in Microsoft 365
Administrators can resolve sign-ins blocked by strong authentication using the following solutions methods.
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Unblock user account in the Microsoft 365 admin center
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Enable user account in the Microsoft entra admin center
Solution 1 - Via Microsoft 365 Admin Center
2 minutes
Unblock User in the Microsoft 365 Admin Center
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Sign in to the Microsoft 365 admin center.
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Navigate to Users » Active users and select the affected Microsoft 365 user account.
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Click Unblock sign-in, uncheck Block this user from signing in, and save changes.
Solution 2 - Via Microsoft Entra Admin Center
2 minutes
Enable User Account Status in the Microsoft Entra Admin Center
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Open the Microsoft Entra admin center and go to Entra ID » Users » All users.
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Select the user you want to enable and click Edit properties.
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Go to the Settings tab and check the Account enabled box to activate the user account.
[Alternative] Require Re-register Multi-Factor Authentication in Entra ID
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Sign in to the Microsoft Entra admin center.
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Navigate to the Entra ID » Users » All users.
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Select the affected user and then choose Authentication methods from the left pane.
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Click Require re-register multifactor authentication to reset the user's MFA.
User Troubleshooting
Steps to Troubleshoot Error 500121 for Users
As a Microsoft 365 user, you can address the strong authentication failed issues using these preliminary steps:
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Clear Browser Cache and Cookies: Clear your browser’s cache and cookies, then try signing in again to resolve potential browser-related problems.
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Set Up Alternative MFA Methods: If the Authenticator app isn’t working, switch to an alternative MFA method, such as SMS codes or hardware tokens.
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Update or reinstall related apps: Ensure your browser and other related applications are up to date. If the issue persists, uninstall and reinstall the affected app to fix potential compatibility or configuration issues.
If the issue continues after these steps, contact your system administrator for further assistance.
Still Need Help?
If these solutions don’t resolve your issue, share your concerns in the 'Discussion forum', and we’ll assist to the best of our ability. However, if none of the solutions work, you may need to contact Microsoft Support for further assistance.