Error 399287 while signing in to school account

Thank you @Max, for the additional information.

I completely understand why this situation feels frustrating, especially when access to your exam results depends on an account that you can no longer access.

Based on your description, this appears to be a school-managed Microsoft 365 account. Unfortunately, Microsoft Consumer Support cannot directly modify or recover accounts that are owned and managed by a school or organization. Every Microsoft 365 Education tenant has at least one administrator who is responsible for managing user accounts, passwords, sign-in methods, and MFA/phone number verification settings.

Even if you are unable to identify the administrator yourself, the account owner organization (your school) remains responsible for providing support to its students. If the phone number used for verification is no longer available or has been flagged, only a school administrator can reset or update those authentication methods.

Here’s a helpful guide to locate your Microsoft 365 administrator: How do I find my Microsoft 365 admin? - Microsoft Support  

You can start by contacting the person who originally provided your account, such as a teacher, school administrator, or IT support staff. If you are unsure who to reach out to, begin with a teacher or staff member you regularly interact with; they can assist you or direct you to the appropriate department. Additionally, check whether your school has a helpdesk portal, support email address, student services office, registrar's office, or technical support channel that can help escalate the issue internally.

Once the appropriate school department is involved, they can either resolve the issue directly or contact Microsoft's organizational support on behalf of the school if additional assistance is required.

Although you mentioned that this is a school account, if you'd like me to help verify the account type, you can send the full email address in a private message. I can check whether any support options are available for the account and advise you on the appropriate next steps.

To access the private message, please refresh this page, you should see a pop-up at the top of your thread. Click on View message to review it. 

I realize this may not be the answer you were hoping for, but because the account belongs to the school's Microsoft 365 organization, there is unfortunately no direct path for Microsoft to bypass the school's administration and modify sign-in or verification settings for an individual end user.

If you need any further assistance please don't hesitate to leave a comment.

Thank you for your cooperation so far!

Thank you for providing the information in our private message, @Max.

I can confirm that your account is managed by your school. As a result, there should be an administrator at your institution who is responsible for assisting with account access and related issues.

As mentioned in Stefan Blom's answer, your school is Microsoft's primary customer in this case, and only the school's IT administrator or authorized representative can contact Microsoft Support on your behalf regarding account-related concerns.

If you have been trying to reach your school's support team through online channels without success, you may want to visit the school's office or IT department directly. Speaking with them in person could help expedite the resolution process.

I hope this information helps. Please feel free to provide an update if you have any new information or questions.

Thank you again for reaching out, and I wish you the best in getting this resolved.

Hello @Max,

Thank you for providing those details. I understand how frustrating it can be to lose access to your school account, especially when you're being blocked by Error 399287.

Based on similar cases, Error 399287 is often associated with a Microsoft identity verification or MFA-related block, sometimes referred to as a "BadReputation" flag on the verification method.

I’d like to clarify that as a forum moderator, I do not have access to user sign-in logs, cannot reset MFA, revoke access, or contact Microsoft Support on your behalf. Please consider me an end user as well, providing guidance based on experience and documented processes. 

To better understand your situation, could you please clarify:

• Could you please help me understand why the school is unable to assist in this situation? For example, are you unable to contact the IT team, or is there no administrator available to help?
• Are you an end user or an administrator for the school's Microsoft 365 tenant?
• Is there another administrator who may still have access to the environment?
• Was the Microsoft 365 subscription purchased directly from Microsoft, or through a partner/reseller?

In many cases, your tenant admin can resolve this by revoking the user’s MFA methods and requiring them to set up MFA again. Here’s how an admin can do that: 

• Go to Microsoft Entra Admin Center: https://entra.microsoft.com  
• Navigate to Users > All Users.  
• Select your user account.  
• Go to Authentication Methods.  
• Click "Require re-register multifactor authentication".  

This action clears out the user’s existing authentication methods, including phone numbers, Microsoft Authenticator registrations, and software OATH tokens, and prompts them to set everything up again during their next sign‑in. 

If the issue continues after the reset, the Global Administrator should open a support ticket so a Microsoft Technical Support Engineer can investigate further. Microsoft Support can check and clear backend blocks when needed. For instructions, you can refer to: Get support - Microsoft 365 admin | Microsoft Learn   

If you are the only administrator in this tenant, please follow the instructions below carefully to escalate your case directly to the Data Protection team:

1. Find the related hotline number for your country to call the frontline and let them raise a ticket for you: Customer service phone numbers - Microsoft Support 

2. Depending on your country or region:

For some countries, when calling the support number, although there are about 30 seconds opening as something "you can visit the link...." But you can ignore this opening and wait until the option, then "1" as a business email user, "1" again for technical help.   

For some countries, it will be an automated conversation like:    

• First, when you call the hotline, it asks what kind of problem you are worried about.   
• Answered: authenticator.   
• A: What kind of product are you using?   
• B: Microsoft 365 for business.   
• A confirmation: education or company account?   
• B: For companies   
• A: Are you an administrator?   
• B: Yes.   
• A: Do you have the other admin in your organization?   
• B: No.   
• A: You need one.... Service request?   
• B: Yes   

Note:

• You may need to call multiple times before you are connected to a live support representative and can successfully create a support request with a ticket number for tracking. 
• If your subscription is from a partner or reseller, contact the reseller's support provider to help open a service request on behalf of you instead.   

If you still need further assistance, please let me know the answers to the questions above so I can better understand the situation and guide you through the appropriate next steps.

Thank you for your understanding, and I look forward to your response.

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