Principled BSDF and Glass BSDF black in GPU Cycles viewport rendering When I use CPU everything works fine, but when I switch to GPU all materials using Principled BSDF or Glass BSDF shaders go completely black in the viewport rendered view; all other shaders seem to work fine. I am using Cycles in blender 2.83 and my graphics card is a GeForce RTX 2060, which I just updated.
I don't know if you solved this, but I had a similar issue until I realised that I had Transmission Bounces set to zero (not Transparency bounces as mentioned in your comment above) ...