Cannot login to https://login.microsoftonline.com/

Question

1. Error Code: 399287
2. Request Id
3. Correlation Id
4. Timestamp
5. tenant [PII removed].onmicrosoft.com

Answer 1

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data. 

Hi TMHCM Pham Ngoc Doanh ******@tenmagroup.jp

In your situation, you should contact your organization’s IT administrator first and ask them to reset your MFA settings by following this article: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID | Microsoft Learn (Microsoft does not have direct access to reset authentication settings for school/organization-managed accounts). After your MFA has been reset, you can try logging in to https://login.microsoftonline.com/ again.

If you are the only Global Administrator and you are completely locked out from the tenant. So, only Microsoft Support team can help you in this MFA issue. You might need to contact Microsoft via phone service number: Customer service phone numbers - Microsoft Support. The agent will be able to create a ticket for you under the affected tenant and then transfer this ticket to Data Protection team who could help you to regain access.  

(Note: We're not Microsoft support, this is a user-to-user support forum. Moderators have no backend access and cannot directly intervene in Microsoft products. We provide only technical guidance and best-practice recommendations based on reported issues)

Additionally, I noticed that your username appears to include personally identifiable information (PII). For your privacy and security, you may want to consider changing your username to better protect your personal information.

I hope this information helps.

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Answer 2

Error 399287 indicates that Microsoft Entra has blocked the phone number for SMS verification because it has been flagged with a “bad reputation.” This prevents completing SMS-based MFA and therefore blocks sign-in at login.microsoftonline.com.

The resolution requires intervention from Microsoft support (Data Protection / Microsoft Data team) to reset MFA and clear the block on the phone number. This cannot be fixed through self-service.

Action steps:

1. Contact Microsoft support by phone and have a frontline agent open a ticket to the Microsoft Data / Data Protection team for the tenant [Moderator note: personal info removed]
2. Clearly state that:
   • Sign-in to Microsoft cloud services fails when using SMS verification.
   • Error code is 399287 and the phone number has been blocked for SMS verification due to “bad reputation.”
   • MFA reset and removal of the phone-number block are required.
3. Work with the Data Protection team until they confirm that MFA has been reset and the SMS block removed, then retry sign-in.

If the tenant has a partner/reseller, that partner can also open a support request on behalf of the tenant administrator.

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References:

• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A

Answer 3

I contacted the reseller, and they helped me reset my MFA. I've successfully logged in now, thanks!

Answer 4

how to login https://login.microsoftonline.com/ when the Authentication not receive a code of the account