Rhino render issue

I have a closed polysurface that does not want to render completely(you can see inside of the solid) There are no non- manifold edges or naked edges or anything like that. What causes this?
Thank you,George

Hi George,

It would be good to see a render and the file to know for sure but at a first guess… It sounds like a flipped normal which wouldn’t be possible if the object were closed. Post an example and I’ll try to help more.