Error 422 at Login time

I have use GtiLab with In house before 2 days it’s working fine but suddenlly portal showing error " 422

The change you requested was rejected.

Make sure you have access to the thing you tried to change.

Please contact your GitLab administrator if you think this is a mistake."

I really don’t know where can i check and fix it same.
Please let me know, I really need help on this