I found a strange behavior on two remote desktop servers at a customer today. They were 2 windows Server 2012 with remote desktop role installed. They were setup with a GPO telling what RD license server to use and what mode to use. Everything looked ok in the RD Licensing Diagnoser and the servers issued licenses to users.
Today, when the 120 days grace period ended, no users could log on. The error message said that there were no licensing servers available.
The solution was to take ownership on the registry key HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Grace Period and then I gave administrators full Control on it and then I deleted it. After a reboot the server worked fine again as a Remote Desktop Server.