Disconnected sessions which are hosted on Server VDA are not logged off.
Apply the following policies from the GPO:
Computer configuration > Policies > Administrative template > Windows component > Remote Desktop services > remote desktop session host > session time limits >
"Set the limit for disconnected sessions"
"End session when time limits are reached"
Wait for the time specified in the policy.
Disconnect sessions are logged off after the time interval is reached.
Policies are not in place.