My workplace has ANSYS EM 18.1 installed on a Linux server workstation with the following CPU/RAM/GPU specs:

-Intel Xeon E5 2670 (x2), 96 GiB DDR3, AMD FirePro V5900;

This machine runs CentOS 6.10, is mostly accessed via SSH and VNC, and lacks VirtualGL. HFSS use over VNC is most convenient, as there are multiple users located in a different building, but doing so means they will not be able to see their renderings: when an HFSS project is launched in a VNC connection, the render subwindow turns black, then flashes briefly if the cursor is clicked and dragged over it. Launching HFSS during a local access session is normal (that's what users are forced to do at the moment, but this situation is highly inconvenient).

Bash console output does not indicate anything.

What might the fix be?