Sorry, we're having trouble verifying your account

Error 399287 during SMS verification indicates a problem with using SMS as the verification method, similar to a known issue where the phone number or SMS channel has a bad reputation or is blocked.

Because Microsoft Authenticator was deleted and SMS is failing, the only supported ways forward are:

1. Try a different verification method (if available)

• On the verification screen, choose Other verification options or any alternative method offered (backup email, different phone number, etc.).
• If another method works, sign in and immediately:
  • Add a new, working security method (new phone number, email, or re‑set up Microsoft Authenticator).
  • Remove or update any outdated phone numbers.

2. If no verification method works for a Microsoft account (personal)

• Go to the Security basics page and select Update info using a method that still works, or choose I don't have any of these and follow the prompts to replace security info.
• If verification codes are not arriving at all, follow the guidance under “I'm not getting my Microsoft account verification code” to:
  • Use a private/incognito browser session.
  • Access the alternate email in a separate private window and copy the code back to the original sign‑in window.

3. If this is a work/school (Entra ID / Microsoft 365) account and you are an end user

• Contact the organization’s Microsoft 365/Entra administrator and ask them to reset your MFA:
  • In Entra admin center, they can go to Users → All users → [your user] → Authentication methods → Require re‑register multifactor authentication.
  • After that, sign in again and set up Microsoft Authenticator (or another method) from scratch.

4. If this is a work/school account and you are the only admin

• Microsoft Data Protection team must assist with unlocking the admin account and MFA:
  • Call the regional Customer service phone numbers - Microsoft Support and have a frontline agent open a Data Protection ticket.
  • Clearly state that this is a business/organization account, you are the only administrator, and you are locked out due to MFA (Authenticator deleted and SMS failing with error 399287).

5. If no method works and you still cannot sign in

• Use the official sign‑in helper for Microsoft accounts and follow the flow for “Can’t sign in?” issues.
• If still blocked, go to Contact Microsoft Support, describe that SMS verification fails with error 399287 and no other MFA option is available, and request escalation. Note that support agents cannot send verification codes or directly change security info; they can only guide through supported recovery and, for work/school tenants, route to the appropriate back‑end teams.

In summary, resolving this requires either:

• Using an alternative verification method to get back in and reconfigure MFA, or
• Having an admin (or Microsoft Data Protection/support for a lone admin) reset MFA or assist with account recovery when all methods are blocked.

References:

• Troubleshoot Microsoft verification code issues
• "Account verification system is having trouble" error message when you try to sign in by using a work or school account
• 399287 - Microsoft Q&A Unable to Verify Identity for Azure Login – Error 399287
• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A
• Microsoft authenticator sending me into a spiral - Microsoft Q&A