Tested on Windows ServerⓇ 2012 R2 Standard.
- Run regedit as the Administrator.
- Go to HKEY_LOCAL_MACHINE -> SYSTEM -> CurrentControlSet -> Control -> Terminal Server
- Double-click on the fSingleSessionPerUser variable and change it’s Value data from 1 (true) to 0 (false)
Later, if you will connect to a user that has multiple disconnected sessions, you will have to choose one to sign into.
There seem to be a hardcoded limit in the windows server that only allows two sessions to run at a given time. When two sessions are running, if a third user connects it will receive this dialog and can ask one of the other users to leave it’s session so that this new guy can use that session.
If you want more sessions it seems that you have to buy some license for each new session that you need to create, or buy another windows server license, install the server on another hardware and have the users connect there, but then you have to sync the servers somehow.
It seems that in order to increase this limit of 2 sessions, you need a Terminal Server Licence.