When I was trying to add a remotefx video adapter to a VM running on Windows Server 2012 R2 I got an error message
Error applying RemoteFX 3D Video Adapter Changes.
And what is that? Well clearly its a GUI bug as I see several other have the same issues as well.The solution was to run this command from PowerShell
Import-Module RemoteDesktopServices
Add-VMRemoteFx3dVideoAdapter -VMName nameofcomputer
SET-VMRemoteFx3dVideoAdapter –VMName nameofcomputer
After that the adapter worked as it should 