Sometimes you may see an error while logging into a terminal server via RDP connection saying that your license has expired or cannot be renewed, or that there aren't enough licenses. This can occur if you've reloaded or changed something on the terminal server. You can delete the License000 registry folder on the client machine, reboot and you should be able to login.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSLicensing\Store]