Error Code: 399287

Question

I'm trying to use SMS as the 2fa to login but I receive this error code. What should I do? Moved from: Azure Advisor

Answer 1

Hello @Andreas Drangel

Welcome to the Microsoft Q&A Community! 

I’m really sorry you’re still stuck after trying all those steps. I know how stressful it is when you need to get in and nothing seems to work. Thank you for hanging in there and for sharing the error details so clearly, that really helps. 

Error 399287 appears when Microsoft’s security system blocks SMS verification because the phone number has been flagged with a “bad reputation.” This is managed by the Microsoft PhoneReputation service and can occur even if your number is valid. 

This block prevents SMS codes from being sent or accepted and cannot be resolved by typical troubleshooting like restarting your phone or resetting your password. 

To make sure I get you back in as quickly and safely as possible, could you please let me know whether the account you’re trying to sign in with is a work/school account or a personal account? If it's a work/ school account, do you have standard user or admin permission? 

If you have a user account, kindly ask the one who is having the Admin permission to help you reset your MFA settings through the Microsoft Entra Admin Center. 

If you’re unsure who the Admin is within your school, you can find guidance on locating them here: How do I find my Microsoft 365 admin? - Microsoft Support 

Please have your administrator follow the steps shown in the following article: Manage authentication methods for Microsoft Entra multi-factor authentication - Microsoft Entra ID … 

• Go to Microsoft Entra admin center > Users > Your Name > Authentication methods 
• Remove the old Authenticator registration 
• Select Require re‑register MFA 
• Save changes 

In case you are the only global admin and cannot access the admin center, you’ll need to contact Microsoft’s official support hotline for your region, listed under the Customer service phone numbers page. They can help verify your identity and reset your MFA methods. 

If you cannot successfully speak to a support representative, please consider creating a new tenant by signing up for a trial Microsoft 365 subscription via this link Compare All Microsoft 365 Plans | Microsoft.  

Once the new tenant is set up, use its admin console to submit a support ticket requesting assistance for your original tenant. Remember to cancel the trial subscription after the issue is resolved to avoid charges.  

I hope these steps help resolve your issue. Please let me know if you have any additional questions or need further clarification.  

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.