Sometimes, the GUI fails to point your Session Host to the License Server. You can manually force this via the registry:
This grace period is not a bug or an oversight; it's a deliberate feature designed for legitimate evaluation and setup. However, once this period expires, clients will be locked out, and users may encounter errors like the dreaded "There are no Remote Desktop License Servers available" message.
If your server reports that the "Licensing mode is not configured," you can force these settings via the registry instead of using Group Policy.
To manually point an RDS host to a specific licensing server via the registry: