Short answer List active and disconnected sessions before acting on the correct one.
When to use it
For stuck RDP sessions or session-limit problems.
List sessions
quser /server:<COMPUTER_NAME>
qwinsta /server:<COMPUTER_NAME>Note
Shows session ID and state.
Log off one session
logoff <SESSION_ID> /server:<COMPUTER_NAME>Note
Unsaved work can be lost.
Caution
Notify the user and assess impact before logging off a session.