Microsoft 365 error code: 500121

Situation: When attempting to login Office.com, you my receive this message:

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

Error Code: 500121
Request Id: ffd712fe-f618-43f9-a889-d6ee74192f00
Correlation Id: 611034c0-111f-40f1-92ee-97c44b855261
Timestamp: 2021-03-16T08:23:50Z

Resolution 1: Click on get code a different way.

Resolution 2: Have Microsoft 365 Global administrator resetting MSA. In multi-factor authenticator, check Require selected users to provide contact method again and Delete all existing app password generated by the selected users.

Or go to Azure portal>Home>Company name>Users>Users>User name.

Resolution 3: Unlock a blocked user.

1. Login Azure portal.
2. go to Home>Security>Security>Ricky users,
3. Remove the user from risky users.