Getting a message that a workstation is still in session, even though I have shut it down completely and restarted.

Shutting down a computer will not clear out an error. It is committed to memory.

You must use that session to enter the screen in your error message that is causing the problem and then EXIT out.

Pull up the workstation that is showing still in session and using that session pull up a customer. Click UPDATE and then EXIT. That will log that session out to a menu.