You can click Sign-in options at login screen, then select PIN, or password or any other sign-in option to login. Then re-setup Face login.
If issue still persists, see if this fix helps you:
https://www.kapilarya.com/fix-facial-recognition-not-working-in-windows-11-10
Let us know if this helps!
Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.