• Then if it still remains check if the account is actually on Azure AD ,as this error can occur when the user credentials you are trying to use does not belong to the same tenant where the application is actually registered in.
• If it is different tenant and you are trying to access from different account, then you may need to change its supported account types to any organizational directory or you need to check for correct credentials. If not check everything or create a new app registration .
• Also please check this blog – Dev – RotaDEV.com for possible ways to solve the issue.

Else you can raise a support request

References:

1. msal - MsalException: Applicationis not configured as a multi-tenant application. Android - Stack Overflow
2. Use single-tenant Azure AD apps with Microsoft Graph Toolkit - Waldek Mastykarz