Although I have purchased 5 CALs for my 2012 Remote Desktop Server, they expired today and no one could use it. Very odd. On closer inspection I had an error saying:
Set the mode on the Remote Desktop Session Host to either Per User or Per Device.
Fine, I will. So I went off to find where in the GUI you can do this. After 30 minutes of fruitless effort, I caved. Everywhere on the web tells you where to set this for 2008, which it does at initial configuration but on 2012 I really struggled. Right, PowerShell it is then:
It spat this at me:
Right, so, just set that then:
Set-RDLicenseConfiguration -Mode PerUser
And voila, fixed it.