This sure resembles the issue where someone changes the linux user fog’s password, or they are using this linux user fog for system administration.
I do have a tutorial on how to resync the linux user fog so you can get past this step: https://forums.fogproject.org/topic/11203/resyncing-fog-s-service-account-password
Understand this is for the linux user fog that is FOG’s service account not the webui default admin by the same name.