Error_code_399287

Question

Issue with Call/Text authentication (Error Code: 399287)

Answer 1

Error code 399287 indicates that Microsoft Entra has blocked the phone number for SMS/call verification due to a bad reputation or unusual/risky activity associated with that number.

This typically results in call/text MFA failing even though the number is correct and working. Because this is a reputation/block issue on the service side, it cannot be fixed by changing local settings or retrying repeatedly.

To resolve the issue:

1. Do not keep retrying SMS/call
   • Excessive or repetitive requests for verification codes can cause or prolong blocking due to unusual activity.
2. Use an alternative verification method if available
   • If Microsoft Authenticator or another MFA method is already configured, select Other verification options at sign-in and use that method instead of SMS/call.
3. Have a Microsoft Entra administrator reset MFA for the affected account (if this is a work/school tenant)
   • A Global Administrator in the tenant can require the user to re-register MFA methods so a different phone number or Microsoft Authenticator can be configured. See: manage user authentication options in Microsoft Entra ID.
4. If the user is locked out and no admin can fix it (or this is the only global admin)
   • A support ticket must be opened with Microsoft so the Data Protection team can reset MFA and clear the bad-reputation block on the number/identity. Community answers show this is how similar 399287 cases were resolved.
5. If this is a personal Microsoft account scenario
   • Follow the guidance for blocked/failed verification codes (avoid repeated requests, ensure a valid mobile—not VOIP—number). If still blocked, contact Microsoft support so they can review and clear the block on the account/number.

In all 399287 cases in the provided material, resolution required Microsoft support intervention (Data Protection team) to reset MFA and/or clear the block; local troubleshooting alone was not sufficient.

---

References:

• Troubleshoot Microsoft verification code issues
• Authentication methods in Microsoft Entra ID - Voice call
• "We didn't receive a response" error message when you try to sign in by using Azure Multi-Factor Authentication
• Troubleshoot Azure Multi-Factor Authentication issues
• Error Code: 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• Azure has blocked myphone number for SMS verification due to a “bad reputation” flag - Microsoft Q&A I try to login via SMS because my phone was reset and now I am getting:
• I need to reset my mfa methods - Microsoft Q&A I need to reset my mfa methods because i reset my phone and cant get to my authenticator app, maybe if i can add a phone number to my account
• Severity A Situation - Locked out of global admin account (MFA) - business down - Microsoft Q&A Got a new phone, and can't access my Microsoft Authenticator app from the old phone. Locked out of the account. Business down. There is only one global admin on the account. Have all business documentation and information.