On a Server 2012 RDS farm that has been deployed and working for some time you begin to receive errors stating ‘The remote session was disconnected because there are no Remote Desktop License Servers available to provide a license. Please contact the server administrator.”
You verify your configuration is as expected, that you have valid CALs installed on a Server 2012 terminal server licensing server and that the RD Licensing Diagnoser doesn’t report any errors.
The issue may be that there is a bug with Server 2012 RDS session hosts where they will not look to the licensing server for CALs when the grace period ends. Microsoft are reportedly aware of this but as yet there is no KBA or hotfix for it.
The solution is to open the registry editor on the affected session hosts and browse to the following:
If the ‘GracePeriod’ key exists you will need to delete it.
Note: You will need to give administrators read and write access to the key or you won’t be able to delete it. *(Must take ownership before changing permissions)* Also please observe the usual precautions when working with the registry and take a backup first.
Give your session hosts a reboot and all should be well.