MS 365 Basis .onmicrosoft.com not accessible

Question

Dear all,

After a reset of the device that previously had the Microsoft Authenticator app configured for the account @.onmicrosoft.com, the account is no longer accessible.

During each login attempt, the system prompts for authentication via either “Approve a request on the Microsoft Authenticator app” or “Use a verification code.” Unfortunately, since the device was reset, we are unable to access the Authenticator app itself to approve the request or generate a code.

Currently, there are no alternative authentication options available, such as email verification or SMS verification, which would allow us to complete the login process.

Could you please advise on how we can regain access to the account or reset the multi-factor authentication settings?

Thank you in advance for your assistance.

Kind regards,

Melo

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Moved from: Microsoft Security | Microsoft Authenticator

Answer 1

Hi @Melo,

Thank you for posting your question in the Microsoft Q&A forum.               

Regarding that you can't log in to your account due to Microsoft Authenticator is. I’d like to ask a quick questions to better understand your situation and assist you effectively:      

Could you please clarify whether you are an end user or an admin?             

If you are an end user I would recommend you contact your account's Admin to reset your MFA settings through the Microsoft Entra Admin Center. Ask your administrator to follow these steps:                 

Revoke MFA sessions and require re-register in the Microsoft Entra admin center                

You could provide your admin this article for a better view: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID |…              

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? - Microsoft Support.  

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.                 

Thank you again for your time and understanding. While my initial response may not resolve the issue immediately, I’d like to gather more details about your situation so I can assist you more effectively.              

I really appreciate your patience, and I’m here to help. Looking forward to your response!                      

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Answer 2

To regain access when Microsoft Authenticator is the only MFA method and the original device is lost or reset, the path depends on whether this is a work/school (Microsoft 365 business) account and whether there is another admin.

1. If this is a work or school (Microsoft 365 business) account and there is another admin
   • Another Microsoft Entra / Microsoft 365 admin in the tenant can reset the MFA settings:
     1. Go to Microsoft Entra admin center (https://entra.microsoft.com).
     2. Navigate to Users → All users and select the affected user.
     3. Open Authentication methods.
     4. Use Require re-register multifactor authentication (or equivalent option) to force MFA re-registration.
   • After this, sign in again with username and password; the sign-in flow will prompt to set up Microsoft Authenticator on the new device (scan QR code, etc.).
2. If this is a work or school account and there is no other admin (you are the only global admin)
   • This is a tenant lockout scenario. In this case, MFA must be reset by Microsoft’s Data Protection team.
   • Call Microsoft global customer service and request a Data Protection / tenant admin MFA reset:
     • Use the phone number list under Customer service phone numbers - Microsoft Support.
     • In the IVR/automated system, clearly indicate:
       • The issue is with Authenticator.
       • The product is Office 365 for business / Microsoft 365 for business.
       • It is a company (not education) account.
       • You are the only administrator and are locked out due to MFA.
       • Ask to create a service request and be routed to the Data Protection team.
   • Be prepared to provide tenant and admin details (admin sign-in name, tenant domain, business information) so they can verify identity and reset the MFA configuration.
   • If direct phone support is hard to reach, one documented workaround is to:
     1. Create a new trial Microsoft 365 tenant (separate from the locked one).
     2. In that new tenant’s Microsoft 365 admin center, go to Support → Help & support.
     3. Open a support ticket explicitly stating that you are locked out of a different existing tenant where you are the only global admin and need a Data Protection team MFA reset.
3. If this is a work/school account and you are an end user (not an admin)
   • Contact the organization’s IT administrator or help desk and ask them to:
     • Reset your MFA settings in Microsoft Entra admin center as described above.
   • After they reset MFA, sign in again and reconfigure Microsoft Authenticator on the new device.
4. If repeated attempts have already been made
   • Multiple failed sign-in attempts or MFA attempts can trigger temporary protection blocks.
   • If seeing messages like “Try another verification method” or similar blocks, wait before retrying and avoid repeated attempts in quick succession, as this can extend the block.

Because there is currently no SMS or email method configured for this account, self-service recovery is not possible; an admin or Microsoft support (Data Protection team) must reset the MFA configuration.

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References:

• Troubleshoot problems with Microsoft Authenticator
• Common problems with two-step verification for a work or school account
• Reset your Microsoft work or school account password using security info
• Troubleshoot Microsoft verification code issues
• 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
• Requesting a Tenant Admin MFA Reset - Microsoft Q&A
• Microsoft authenticator sending me into a spiral - Microsoft Q&A
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A