Hi can you test, if the latest release fixes the issue for you? It does not for mine though. I filed another request a chaos.
I solved all the problems: I had Rhino 8 blocked in the firewall rules.
I removed the block and now Vray works on GPU with every driver (including the latest Vray update).
Turns about this is something different and the bug remains, so 6.20.06 will not fix this problem. Aparently they are still working on it. TBC.
I think this wass some other issue then, but glad to hear it worked for you.