MFA verification methods fail with error 399287

Question

Hi,

I am the only Global Administrator of the Microsoft 365 tenant. I can authenticate with my password, but all MFA verification methods fail with error 399287. I need an MFA reset or backend review of the authentication methods for the account.

Tenant/domän: competit.com

1. User: [Moderator note: Personally Identifiable Information removed] @competit.com
2. I'm the only global administrator
3. Errorcode: 399287
4. Request ID: [Moderator note: Personally Identifiable Information removed] 
5. Correlation ID: [Moderator note: Personally Identifiable Information removed] 
6. Timestamp: 2026-10-14T18:18:41Z

Best regards,

Magnus

Answer 1

Hi Magnus, 

Thank you for sharing the details of your situation.

Based on your descriptions, I recommend contacting Microsoft Support and requesting assistance from the Data Protection team. They can guide you through the tenant ownership verification process and help recover access to the administrator account.

• Please try locating the appropriate hotline for your region 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.      

 

I also recommend calling during business hours. In my experience, it can be difficult to get through to the correct support queue, and automated systems don't always work as expected. If you can't get through on your first try, I suggest trying again later or at a different time. 

  

I hope these steps help you create a support ticket successfully and move closer to regaining access to your administrator account. While I’m not able to intervene directly, guiding you to the right support team is the most effective help I can provide here.  

Hope you're able to get this resolved soon. 

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