MyPC is "Available", but no one can log in system-wide

The Cause

If MyPC shows "Available" on the Status Bar on all Public machines, but you get an error "An Unknown Error has Occurred" for ALL cards including Tech and Staff Users,

The Solution

Check to make sure the 'TBS ILS Service' is running on the server. If it is, try to stop/start it and see if that resolves the issue. Below is a screen show of the error you might see.