Getting this error, was working fine for couple months. Running 2X server application on the dedicated server and running published applications from different server using RDP.
this looks more of a Terminal Server issue. It cannot issue TS licenses to clients that connect to your TS. Check your TS License server and that the TS's can issue licenses to users that connect.
I know this is an old post but I had similar issues with Win8 client and 2x on 2012r2. The solution for me was on client computer, connect to company VPN and then go to Remote Desktop Computer. Right click on Remote Desktop Computer and choose “Run as Administrator”. Log into 2x server then log off. 2x client will work now.