It seems compiling of kernels isn’t going as expected in thumbnail preview rendering.
With the rendering panel hidden set the render device back to your GPU. Then change a viewport to Raytraced and click the running number in the right side of the HUD, change the number to something large, I use generally 999999 for this step. Let Rhino run for 10-20 minutes. You’ll see that after a short while the viewport changes to gray, that is expected.
After the long wait change the viewport to Wireframe and back to Raytraced. If it starts rendering white (or if you have a model open already to whatever it is) the kernel.compiling finished.
You should be able to scroll in the Rendering panel now.