Error 50021

Question

I have been logged out of my accounts in the authentication app since I got a new phone, when I try to log in it gives me error 500121. It’s saying it will send me the authentication codes etc but it didn’t and just leaves me at either the error or waiting page. I need this fixed ASAP so I can sign into my email!!

Answer 1

Hi @Miles Sheehan

Regarding your issue, error code 500121 usually means the sign‑in fails at the MFA step. Your username and password may be correct, but the verification through Microsoft Authenticator isn’t completing (for example, no notification is received or approved). Because of this, the system can’t confirm your identity and blocks access until MFA can be completed or reset.

To help move this forward, may I kindly ask if you have other admin with at least authentication administrator role in your organization? If yes, you can ask them to either unblock your account or reset your multi-factor authentication (MFA) for you.    

They can follow these steps:   

1. Sign in to the entra.microsoft.com as at least Authentication Administrator.   
2. Select User -> All user.   Select the user (your account) to act on and select Authentication methods. then select Require re-register of multi-factor authentication.    

• Require re-register MFA: This disables all previous authentication methods. You'll then be prompted to configure a new MFA authentication method the next time you try to sign in, so you can set up from the start and add a new authenticator app.   

 

For more details, please refer to: Manage user authentication methods for Microsoft Entra multifactor authentication. 

Note: Once re-registration is triggered, all your existing MFA methods such as phone numbers, Authenticator app, or other verification options will be removed. You will need to set up new MFA methods during your next login. Please ensure you have access to a valid phone number or the Microsoft Authenticator app before attempting to sign in again.   

If you’re unsure who the Global Admin is within your organization, you can find guidance on locating them here: How do I find my Microsoft 365 admin?      

Hopefully it will help work with your issue and if you have any other questions or need further assistance, feel free to ask.   

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Answer 2

Follow these steps to regain access and work around the failed Authenticator sign-in and missing codes:

1. Check for blocks or throttling
   • If there have been many failed sign-in attempts, Microsoft Entra multifactor authentication may temporarily block additional attempts as a security measure. In that case, wait and try again later, or use a different MFA method if one is available.
   • If you keep trying repeatedly, it can extend the block window and delay code delivery.
2. Fix issues with verification codes (SMS/email) When it says it is sending a code but nothing arrives:
   • Avoid repeated “send code again” clicks; this can cause a temporary block on sending codes.
   • Check whether the phone blocks texts from unknown numbers and, if so, change that setting and then choose I don't have a code to trigger a new one.
   • Make sure the phone’s SMS inbox is not full and the messaging app is working properly.
   • Do not use a VOIP number; verification codes cannot be sent to VOIP numbers.
   • For email codes, check the junk/spam folder for messages from @accountprotection.microsoft.com and mark that sender as trusted.
   • Confirm that the phone number or email shown (masked) on the sign-in screen is actually correct. If not, the security info must be updated by signing in to the Security info page and choosing Update info (if still signed in somewhere).
3. Troubleshoot the “Authentication did not complete” behavior If the app shows an error or just spins:
   • Make sure the Microsoft Authenticator app is unlocked on the device.
   • Ensure notifications are enabled for Microsoft Authenticator and not set to silent.
   • Install the latest version of Microsoft Authenticator from the store.
   • Verify the device has a working internet connection; if needed, switch between Wi‑Fi and mobile data.
   • Confirm the device’s date and time are correct.
4. If still unable to sign in
   • If this is a work or school account and multiple attempts have failed, contact the organization’s IT administrator or Help desk and ask them to review Microsoft Entra sign-in logs and, if needed, reset MFA methods.
   • If already signed in on another device or browser, use that session to:
     • Update security info (add a new phone/email or method that works).
     • Temporarily disable or change 2FA methods if allowed by the account’s security policy.
5. If completely locked out as the only admin
   • For a work or school tenant where this account is the only administrator and no other MFA method works, contact Microsoft support by phone using the global customer service numbers and request the Data Protection team to help reset MFA for the admin account.

For personal Microsoft accounts that cannot sign in to Outlook mobile because of these issues, use the sign-in helper tool to diagnose and guide recovery, or reset the password if prompted.

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References:

• Authentication did not complete
• Troubleshoot problems with Microsoft Authenticator
• Common problems with two-step verification for a work or school account
• Can't sign in to the Outlook mobile app