MFA & Verification Issues

Reset Microsoft Two-Step Verification After Losing Phone

Elise Williams Sep 25, 2026 869 views

Question details

The user lost their authentication device and is unable to access a school-managed Microsoft account, often resulting in error code 500121.

How to Reset Microsoft Two-Step Verification After Losing Your Phone

Product: Microsoft 365
Device & OS: not provided
Scenario: Attempting to sign in to a managed Microsoft account without access to the primary two-step verification device or phone.
Observed behavior: The system denies access, prompts for a verification code from the lost device, and may display error 500121.

Before you start

Before reaching out to support, check if you previously set up an alternative verification method, such as a backup phone number or secondary email address.

Solution 1Recommended

Contact Your School's IT Administrator

Because this is an organization-managed account, your IT administrator must reset your MFA settings from their end.

School and work accounts have strict security policies managed by the organization. You cannot bypass this security independently if no fallback methods were configured.

Your administrator has the necessary permissions in the Microsoft Entra admin center to reset your session and require you to re-register for MFA.

Locate IT support

Identify your school or organization's IT support desk or administrator contact information.

Request an MFA reset

Contact them and request an MFA session reset, or ask them to "Require re-register MFA" for your specific Microsoft account.

Log in and re-register

Once the administrator confirms the reset, log in to your account. You will be prompted to set up two-step verification again using your new phone or authenticator app.

Administrator Guidance: Administrators can perform this reset via the Microsoft Entra admin center under Identity > Users > Authentication methods.

Solution 2

Sign in Using an Alternative Verification Method

Use a secondary verification method to access your account if you previously configured one.

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Frequently Asked Questions

What does Microsoft error code 500121 mean?

Error code 500121 occurs when authentication fails as part of a multifactor authentication (MFA) request. This usually happens if the device is lost, the user hasn't set up MFA correctly, or the authentication request is actively denied.

Can I bypass Microsoft two-step verification without my administrator?

For a school or company-managed account, you cannot bypass two-step verification on your own unless you previously configured fallback methods like a secondary email or alternative phone number.

How do I update my new phone number for Microsoft Authenticator?

Once your IT admin resets your MFA session, log in to your Microsoft account. You will automatically be prompted to register your new device and update your phone number for future verifications.

Login & Account Issues