Try this:
1. Open Group Policy on Server (Start --> Run --> Type: gpedit.msc)
2. In Computer Configuration, Administrative Templates, Windows Components, Terminal Services, double-click Use the specified Terminal Server license servers
3. Click Enabled
4. Enter the names of the Terminal Server license servers you want this Terminal Server to contact first when attempting to obtain client access licenses (CALs), and then click OK
You may have to restart the server and see if the changes have taken effect.