Error Code: 500121 Request Id: [Moderator note: Personally Identifiab Correlation Id: [Moderator note: Personally Identifi Timestamp: 2026-09-30T03:19:23Z on my Mac when verifying two step authentication using my cell. It worked previously using landline.

Tsing Bardin 0 Reputation points
2026-09-30T03:48:28.9266667+00:00

Previously, I was able to complete two step authentication using my landline, but now I changed to my cell phone which is listed correctly, but it did not receive any text nor call. the error shows Error Code: 500121

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

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

Timestamp: 2026-09-30T03:19:23Z

So why doesn't the cell phone work? the number is correct.

HELP! I need to use my school account to do homework. Neither my school accounts works., one at Yosemite college the other at West Valley college

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  1. JeseminQH 925 Reputation points Independent Advisor
    2026-09-30T04:28:18.7066667+00:00

    Hi @Tsing Bardin

    Error 500121 generally means that the multi-factor authentication request could not be completed. Even if the cell phone number shown in your profile is correct, it may not be properly registered as an MFA method, or text and voice verification may be restricted by your organization’s security settings. Changing the number in your account profile does not always update the number used for MFA. 

    Since these are school-managed accounts, please contact the IT administrator or help desk for each school account separately. Ask them to verify your registered authentication methods and reset your MFA or require MFA re-registration. This should allow you to register your cell phone again. 

    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.    
    • User's image

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

    Find Your Microsoft 365 Admin: If you're unsure who manages Microsoft 365 accounts for your school, please contact your school's IT Help Desk, Technology Support team, or Student Services office, you can find guidance on locating them here: How do I find my Microsoft 365 admin? 

    User's image

    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.    

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

    If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment". 

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  2. AI answer

    2026-09-30T03:48:43.1933333+00:00

    Error 500121 in this scenario usually means the MFA verification is being blocked or the selected method is not succeeding, even when the phone number appears correct.

    Try these steps in order:

    1. On the sign-in screen, select Sign in another way.
      • If the old landline method is still available, use it to get signed in.
      • If another method is listed, such as email or another phone, use that instead.
      • If Sign in another way is not available, no alternate method is set up.
    2. If signed in successfully with another method, go to the Security info page and verify the mobile number.
      • Select Update info.
      • Choose a method that works, or choose I don't have any of these to replace the security info.
    3. If the cell phone should receive SMS or calls but does not:
      • Do not make excessive or repetitive requests, because that can trigger a temporary block.
      • Check whether the phone blocks texts from unknown numbers.
      • Check whether a third-party security app is blocking text messages or calls.
      • Make sure the number is a mobile number, not a VOIP number.
      • If using SMS, choose I don't have a code to request another code.
      • Try up to five times in 5 minutes to receive a phone call or text.
    4. If repeated attempts were already made, wait and try again later.
      • Microsoft Entra multifactor authentication can block additional attempts after unusual or repeated sign-in activity.
      • In some cases, waiting a day helps. If there is still no change after 24 hours, waiting longer may be required.
    5. If neither school account has another working verification method, contact each school’s IT help desk.
      • If no alternate verification method was added, help desk assistance is required.
      • If the phone was changed or the MFA method is no longer working, the organization can clear or reset the MFA settings so registration can be done again.
    6. If the school IT administrator needs to investigate, they should check the Microsoft Entra sign-in logs.

    Because these are school accounts, support agents are not allowed to send verification codes or directly change account details for account recovery. The practical path is:

    • use Sign in another way if available,
    • update or replace the security info,
    • avoid repeated retries,
    • then contact Yosemite College and West Valley College IT help desks if no alternate method works.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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