a grey render is your RTX card crashing on a bad material node or shader in your scene. Once you have that crash you have to restart Poser or it wont render anything at all with OPTIX checked. First thing to check after restarting Poser is turn off OPTIX and see if it renders. If you get a render then you have to figure out what figure or object is causing the crash. Turn off everything in your scene except one thing and see if you get a render or a crash. If a crash then look at the shader setup for that item. One thing OPTIX does not like is ambient occlusion nodes. Super Fly DOES NOT NEED TO FAKE AMBIENT OCCLUSION WITH A SHADER NODE. I have also found that my free Super Shader for P11 sometimes crashes OPTIX.

W10, Ryzen 5 1600x, 16Gb,RTX2060Super+GTX980, PP11, 11.3.740