If several monitors are connected to the PC with the ProCall Enterprise client installed, only the content of one screen can be shared.
Both monitors are available in the screen sharing preview, but show the same content (of the primary monitor).
Terminal Server/Citrix Server does not support Direct3D.
Direct3D support can be disabled on the server where ProCall Enterprise client is installed.
Create registry entry
On the server where the ProCall Enterprise client is installed, create DWORD value "AVScreenCaptureMode" and set it to 1 (decimal).
AVScreenCaptureMode = 1
This disables Direct3D support.
Then restart the ProCall client.