When trying to RDP to a Windows Server from PAM users are seeing "License Server Not Available".
In order to RDP into a Windows Server, with either PAM or native RDP(mstsc.exe), the server must be licensed appropriately. There is a period of time during which the server can be accessed even without a license. After that period expires the system will become inaccessible if a license server is not available. Here are details from Microsoft: https://docs.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-client-access-license#understanding-the-cals-model.