Unable to Verify Identity for Microsoft 365 Login – Error 399287

Louis Udeani 0 Reputation points
2026-11-08T07:38:46.1966667+00:00

Dear Microsoft Support Team,

I'm trying to sign into the Microsoft 365 portal. I can sign in to my Microsoft account, but I'm prompted to verify my identity via SMS. However, I receive the following error message:

“Sorry, we’re having trouble verifying your account. Please try again.”

Error Code: 399287

Request Id:

Correlation Id:

Timestamp: 2026-11-08T07:18:13Z

I have already tried alternative login methods and password reset options but have been unable to complete the identity verification process. I would appreciate your assistance in resolving this issue as soon as possible. It would be great if you could unblock the MFA to the account. I will use the Microsoft Authenticator instead of the SMS verification as I get access to my account.

Thank you for your kind support

Best Regards,

Microsoft 365 and Office | Subscription, account, billing | For business | Other
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  1. AI answer

    2026-11-08T07:39:32.08+00:00

    Another tenant administrator should require MFA re-registration for your account; if no other administrator can access the tenant, Microsoft 365 business support must escalate the lockout for backend MFA unblocking.

    If another administrator can sign in

    Ask an administrator with the required authentication-management role to:

    1. Open Microsoft Entra admin center.
    2. Go to Entra ID → Users.
    3. Select your affected account.
    4. Select Authentication methods → Require re-register MFA.
    5. Select OK.

    This removes the registered phone numbers, Microsoft Authenticator registrations, and software OATH tokens, then requires you to configure MFA again during your next sign-in. It is disruptive to all existing MFA methods on that account, so the administrator should confirm the correct user before proceeding.^1^

    After the reset:

    1. Start a new sign-in session.
    2. Complete the registration prompt.
    3. Select Microsoft Authenticator instead of SMS.
    4. Scan the QR code with the Authenticator app and complete the test approval.

    Since alternative sign-in and password reset have already failed, repeating either process is unlikely to address this MFA verification failure.

    If you are the only administrator

    A sole administrator cannot perform the reset on their own locked account. Contact Microsoft 365 business support using the official regional support page and request escalation for a tenant lockout caused by MFA error 399287.^2^

    Provide these details privately to the support agent:

    • Affected user principal name and tenant domain
    • Error code 399287
    • Request ID and correlation ID
    • UTC timestamp
    • Verification method: SMS
    • Confirmation that password reset and other available sign-in methods failed
    • Confirmation that no other administrator can reset the account, if applicable
    • Request to escalate to the team handling tenant access/MFA backend blocks

    Do not publish tenant identifiers, telephone numbers, or account details in a public Q&A reply.

    The exact same Microsoft 365 SMS symptom and error have previously required Microsoft engineering to clear the backend MFA block and associated phone reputation before sign-in worked again.^3^ Microsoft Q&A moderators normally cannot directly change account authentication state; the supported sole-administrator route is Microsoft support/Data Protection escalation.^4^

    If your organization has a Microsoft partner with active delegated administrative access and the appropriate role, the partner may be able to restore access or open the service request on your behalf.^5^

    After access is restored

    Register Microsoft Authenticator and retain an additional permitted recovery method. For administrator resilience, the tenant should also have a separate appropriately privileged administrator capable of handling future lockouts; Microsoft recommends maintaining a Privileged Authentication Administrator for this purpose.^6^

    References

    1. Manage user authentication methods for Microsoft Entra multifactor authentication
    2. Contact Microsoft customer support
    3. Unable to Verify Identity for Microsoft 365 Login – Error 399287 - Microsoft Q&A
    4. Unable to Verify Identity for Microsoft 365 admin center Login – Error 399287 - Microsoft Q&A
    5. Preventing tenant lockouts
    6. About administrator roles in the Microsoft 365 admin center
    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Roebe Ta 1,825 Reputation points Independent Advisor
    2026-11-08T08:10:03.5366667+00:00

    Hello @Louis Udeani ,

    I’d like to clarify that I don't represent Microsoft, I do not have access to user sign-in logs, cannot reset MFA, revoke access, or contact Microsoft Support/Data Protection Team on your behalf. Please consider me an end user as well, providing guidance based on experience and documented processes.

    The error code 399287 usually indicates that Microsoft has blocked SMS‑based authentication for the phone number or tenant due to a reputation or risk flag. This usually happens when Microsoft detects patterns such as repeated failed attempts or suspicious behavior. Once this block occurs, SMS verification fails even if the number is correct and previously worked.  

    Firstly, try selecting "Use a different way to sign in" or "Sign in another way" on the sign-in page and use another available verification method, such as email or Authenticator verification.

    User's image

    If the issue persists, 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".  

    User's image

    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're an admin, please check to see if there are other admins in your organization who can help you. 

    If you are the only administrator in this tenant, you will need to contact the Microsoft Data Protection team, as they are the only group authorized and equipped with the necessary tools and verification procedures to confirm your identity and restore administrator access. 

    Please try to find the related hotline number to call the frontline and let them raise a ticket for you: Customer service phone numbers - Microsoft Support 

    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 business
    • 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 encounter any difficulties in contacting the frontline support, please feel free to let me know. Thank you and I wish you a great day!

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