Authenticator

Question

Error Code: 500121

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

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

Timestamp: 2026-05-30T09:57:11Z

Veml

Answer 1

Please understand that as forum moderators, we do not have the tools or sufficient access to make changes to user accounts, including logging in, resetting passwords, or modifying access rights. For your security, only Microsoft Support can assist with these requests. However, I will do my best to guide you using publicly available documentation, research, and community experience.  

Hello @Armendariz, Erica

Welcome to Microsoft Q&A Forum!  

To better understand your situation and guide you correctly, could you please confirm whether you are an end user or a global administrator of your Microsoft 365 tenant?  

The next steps will depend on your role:  

1. If you are an end user  

The quickest and most effective solution is to contact your organization’s IT administrator. They can revoke your current Multi‑Factor Authentication (MFA) settings and allow you to re‑register.   

You may share this official Microsoft article with them for detailed guidance: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID |…    

2. If you are an administrator  

Please check whether there is another admin in your tenant. If so, they can reset your MFA configuration by:  

• Signing in to the Microsoft Entra Admin Center  
• Navigating to Users > Your Account > Authentication methods  
• Selecting Require re‑register MFA  

You will then be prompted to set up MFA again at your next login.  

3. If you are the only administrator  

In this case, you will need to contact Microsoft’s Data Protection team, who are authorized to verify your identity and reset MFA settings. Please call Microsoft Support using the appropriate regional hotline listed here: Customer service phone numbers - Microsoft Support  

Here are some tips and an example of a prompt to help you navigate the IVR more effectively:   

(When you call the support number, you may hear an introduction of about 30 seconds such as "you can visit the link...". You can ignore this introduction and wait until you are presented with the options. Then press "1" as a business email user, and again "1" for technical help.)     

In some regions, the initial interaction may be automated, so here’s a general idea of how the conversation might go to help you prepare:       

• What kind of problem are you experiencing?          
• Answer: Authenticator          
• What products do you use?          
• Answer: Office 365 for business          
• Is this for an education or company account?          
• Answer: For companies          
• Are you an administrator?          
• Answer: Yes          
• Are there any other administrators in your organization?          
• Answer: No. I am the only admin in my tenant           
• Do you need a... Service request?           
• Answer: Yes. I need to create a ticket. Please send me direct to the Data Protection Teams.       

During the phone call, you will need to provide the information associated with your subscription, such as your company name, billing details, phone number, and an alternate email address, etc. This information allows the Data Protection team to verify your identity and securely assist you in regaining access to your administrator account.      

Could you please confirm which of the three cases applies to you? Once I have this information, I can guide you further and ensure you get the correct next steps.  

Thank you, and I look forward to your reply. 

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Answer 2

Error code 500121 is an authentication failure indicating that the sign-in request to Microsoft services (such as Microsoft Authenticator-backed sign-in) could not be completed successfully and resulted in an HTTP 500-class error.

From the provided information and similar scenarios in the context, this type of error is typically related to problems with multi-factor authentication (MFA) or the Microsoft Authenticator configuration, especially when changing or losing access to a phone.

Recommended actions based on similar resolved cases in the context:

1. If access to the account is still available on a trusted device (for example, already signed-in Windows PC or browser session), temporarily adjust MFA settings:
   • Sign in to the account security page from that trusted device.
   • Temporarily disable or reconfigure the problematic MFA method (for example, Microsoft Authenticator) and ensure an alternative method (such as SMS or email) is working.
   • Re-add Microsoft Authenticator on the new device and complete registration.
2. If locked out of the only admin account in a business/tenant scenario:
   • This is treated as a tenant lockout. The Microsoft Data Protection team must verify identity and restore access.
   • Open a support ticket with Microsoft (or via a partner/reseller if applicable) and clearly state that the only global admin is locked out due to MFA/Authenticator issues.
   • Provide tenant and admin details as requested by support so they can help regain access.
3. If there are other global admins in the tenant:
   • Another global admin can reset or re-register MFA for the affected account from the Microsoft 365/Entra admin portals.

These steps align with how similar authenticator/MFA lockout and error scenarios are resolved in the referenced cases.

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References:

• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A
• Why can't just use my password anymore to log into my email. been going on for a while.... - Microsoft Q&A
• Cannot authenticate with E-mail when logging into Microsoft Authenticator(iOS). - Microsoft Q&A