Unable to access Microsoft 365 Admin Center due to MFA registered to a former employee

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Dear @NEDEC 관리자

Thank you for reaching out. I understand how urgent this situation is, especially since your business operations are affected by the loss of administrator access.

Since the MFA phone number belongs to a former employee, the recovery process depends on whether your organization has another Global Administrator.

Option 1: If another Global Administrator is available

Ask them to sign in to Microsoft Admin Centergo to the Microsoft Entra Admin Center and follow these steps:

1. Navigate to Entra ID > Users > All users.
2. Select the affected administrator account.
3. Open Authentication methods.
4. Select Require re-register MFA to reset the existing MFA registration.
5. Have the affected administrator sign in again and register a new authentication method.

Please refer to this document: Manage user authentication methods for Microsoft Entra multifactor authentication

If there is no other Global Administrator

Option 2: If this is your organization’s only Global Administrator account, Microsoft Support will need to assist with tenant ownership verification and MFA recovery.

Since you cannot access the Microsoft 365 Admin Center, I recommend contacting Microsoft Business Support through the official regional telephone numbers

Explain that your organization is experiencing a sole Global Administrator MFA lockout and request assistance from the appropriate Data Protection / Tenant Recovery team.

If telephone support is unsuccessful, you may also consider creating a temporary Microsoft 365 Business trial tenant to access the Admin Center and submit a support request for your original tenant.

Once signed in to the temporary tenant, navigate to Help & support, explain that the issue concerns your original organization, and request assistance with tenant ownership verification and administrator MFA recovery.

Please note that the temporary tenant is only a possible route to contact support; it will not automatically restore access to your original tenant. You should also check the trial’s cancellation date to avoid unintended charges.

Microsoft’s official guidance: Get support for Microsoft 365 for business

Important: Microsoft may request proof of domain ownership, subscription invoices, or billing details to verify your organization. Please provide these privately to Microsoft Support, not in this public forum.

As an Independent Advisor, I cannot directly reset your administrator’s MFA or escalate the case internally, but I hope these steps help your organization regain access.

Could you please confirm whether this is your organization’s only Global Administrator account? This will help determine the appropriate recovery path.