After installing the licenses on your Windows 2008 R2 and upper for Terminal services and activated both the license and server you might have a popup message saying No Remote Desktop license server is specified. Also when you open the Remote Desktop Session Host Configuration you might see a similar message under the licensing diagnosis.
To fix this issue you must specify the Remote Desktop Services License Server. This can be done by the following:
Open the Remote Desktop Session Host Configuration from the Administrative Tools
Left click on the RD Session Host Configuration node
Double click on the Remote Desktop license servers
Add the server where the licenses have been installed
This should solve the issue and stop the message from showing