This article refers to situations when admin users or regular users logged of from RDP session without actually pressing the "Logoff" button.
To identify the connected sessions try this:
1. Open command prompt.
2. Type qwinsta /server:Server IP Address
3. You should be getting a table with Sessions, state and ID.
4. Write down the ID of the user you want to logoff.
5. Type rwinsta /server:SERVERIP SessionID from Section 4