Unable to Access Microsoft 365 Admin Account - Error Code 399287

Hi @Gowardun Vimal,

Thank you for reaching out to Microsoft Q&A forum. We are happy to assist you.

Error Code 399287 typically occurs during multi-factor authentication (MFA) when:

• The phone number used for SMS verification has been flagged by Microsoft Entra's PhoneReputation service due to suspicious activity or poor reputation.
• There have been multiple failed login attempts, which can trigger a temporary block.
• You're the only global admin, and no fallback MFA methods are configured.

Here're suggestions you can try to fix your issue:

1. If other admins exist in your organization, please ask them to temporarily disable MFA for your account so you can regain access and reset MFA settings.
2. If only 1 admin account, advise Call to service phone number & contact partner, reseller   

Based on the details you have shared. It seems that you are in a difficult situation with your Microsoft 365 account and administrative access.    In this situation, the Microsoft Data Protection team has tools and processes in place to verify identity and regain access to administrator accounts.   

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.   

Therefore, 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. 

3. Another workaround 

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 hope this information will be helpful for you. Please feel free to reach out if you have any further questions or need assistance! 

Thank you for your patience and understanding. 

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