Posted 11 May 2017 - 06:46 PM
I had the same issue, but maybe with a different underlying cause and a solution:
I set up a new XenDesktop 7.13 site with some Windows 10 machines. All machines are running on one XenServer 7.1 host. Two of these VMs are using the Tesla Grid M60 in the host. Because it was not yet decided if the other VMs also need the Tesla graphics support, I installed the Nvidia Grid driver in all of the machines, but didn't assign a vGPU in XenServer. During installation of the Virtual Delivery Agent I also checked the button to use HDX 3D Pro on all the machines.
The two machines with vGPUs assigned are running fine. But the others showed a grey frame in full screen mode and also in windowed mode when I resized the Desktop Viewer window. Sometimes I also had issues with mouse offsets. This happened with Citrix Receiver 4.7 as well as with Receiver 4.4.4000 for Windows LTSR CU4.
Long story short: I uninstalled the Nvidia Grid driver from the non vGPU machines, which did not solve the problem itself. Then I also removed the Virtual Delivery Agent and reinstalled it, this time with standard VDA not HDX 3D Pro. Everything seems to work now.
I hope this might help someone.