How to reset the Cal assigned to the remote PC (Unable to Connect error):
If a client is unable to connect to the terminal server due to a licensing issue, you can delete the MSLICENSING key on the affected machine. This will reset the license at the client so then it will pick up a new License from the TS:
In the registry,
go to HKEY_LOCAL_MACHINESOFTWAREMicrosoftMSLicensing;
delete the MSLicensing key