Ran across this issue today, User had unresponsive session in Citrx, support had tried to log off the user, or reset the session from appcenter. The session would appear to be gone, but reappear after a refresh. After digging a bit, we did not see a session on remote desktop manager, nor did it appear in task manager under the users tab.
The fix turned out to be quite simple:
1. open the task manager, navigate to the processes tab.
2. click the view menu at the top of the window and click “select columns”
3. click the checkbox next to “session ID” and click ok.
4. open the app center and find the session id for the affected user.
5. locate the session id in the task manager and kill all processes that match that session id.
Most likely these processes were holding up the session. In our case it did solve the issue and the user was now able to logon without further incident.