need global mfa help

Question

I am the Global Administrator of a Microsoft 365 tenant for elitefireandsecurity.com.

The tenant was just released from GoDaddy to direct Microsoft management.

I cannot sign in because MFA is requiring Microsoft Authenticator and SMS to an old phone number that I no longer have access to.

I need an MFA reset for the Global Admin account.

Error Code: 500121.

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Moved from: Microsoft 365 and Office | Microsoft Family Safety | For home | Windows

Answer 1

Dear @Elite Fire And Security,

Welcome to Microsoft Q&A. 

Thank you for sharing the details of your situation. I’m sorry for the disruption this has caused, being locked out of a Global Administrator account can be very stressful, especially when MFA is involved.

Based on what you described, the sign‑in failure with error code 500121 is occurring because the MFA challenge cannot be completed. Since your Global Admin account is still configured to use Microsoft Authenticator and SMS tied to an old phone number, the authentication step cannot be satisfied. This behavior is by design and is part of Microsoft’s security protections. When MFA cannot be validated for a Global Administrator, access is intentionally blocked to protect the tenant from unauthorized changes.

Because this is a Global Administrator account, MFA settings cannot be reset by the affected user themselves. If another Global Admin exists and can still sign in, they can reset or require re‑registration of MFA for your account from the Microsoft Entra admin center.

Please have your administrator follow the steps shown in the following article: Manage authentication methods for Microsoft Entra multi-factor authentication - Microsoft Entra ID … 

Please note that forum moderators have no control over user accounts, especially when it comes to logging in to your account, resetting your password, changing your access, etc.

If you are the only administrator in your organization, then you need to involve Microsoft data protection team.

Please try to find the related hotline number to call the frontline let them raise a ticket for you: Customer service phone numbers - Microsoft Support 

In some countries, this is an automated conversation: First, when you call the hotline, they will ask you what kind of problem you are struggling with. 

Answer: Authenticator. 

A: What products do you use? 

B: Office 365 for business. 

Verification: Education or company account? 

B: For companies 

A: Are you an administrator? 

B: Yes. 

A: Are there any other administrators in your organization? 

B: No. 

A: I need one.... Service request? 

B: Yes 

  If your organization's Office 365 Business/Education subscription is from a partner or reseller, and the global administrator is unable to open a service request on your end, contact the reseller's support provider to help open a service request on behalf of you instead. 

 

If you still cannot reach to agent, there is still a workaround, you might consider registering for a new tenant by signing up for a trial subscription via this link Compare All Microsoft 365 Plans | Microsoft. This would allow you to create a new tenant following the provided prompts. Once set up, you can access the admin console of the new tenant and submit a support ticket requesting to speak with the Data Protection team on behalf of your previous tenant.  

Please remember to cancel the trial subscription once your issue is resolved to avoid any unintended charges.  

I understand that this entire process can feel long and complicated, and I truly appreciate your patience while working through it. These steps are in place to protect the security of your account, so I hope you can understand why they are required. I sincerely hope you’ll be able to regain access to your account soon. If you need help at any point, or if you have any questions during the process, please feel free to reach out, I’m always here and happy to assist.  

Thank you again for your understanding and patience. 

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Answer 2

To reset your Multi-Factor Authentication (MFA) for your Global Administrator account, you will need assistance from another Global Administrator or Microsoft support. If you are the only Global Administrator and cannot access your account due to the MFA requirements, here are the steps you can take:

1. Contact Microsoft Support: Since you are locked out, you should reach out to Microsoft Data Protection Support. They can help verify your identity and reset your MFA settings. You can do this by calling their customer service and explaining your situation.
2. Alternative Administrator: If there is another Global Administrator in your organization, they can log in to the Azure portal and reset your MFA settings. They would need to navigate to the user's blade, select your account, and click on "Require re-register multifactor authentication".
3. Documentation: Refer to the Microsoft documentation on managing user authentication options for further guidance on resetting MFA settings.

Make sure to provide any necessary details to support to expedite the process.

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References:

• I need to reset my mfa methods - Microsoft Q&A
• Global Admin Locked out - Microsoft Q&A
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A