Export FBX problems with stp files and block instance


I received two stp files from a friend. I added these parts to my Rhino model. Now I want to export the whole model as FBX for e.g. Keyshot, but a mesh is not created as usual. I get an fbx file without an error message, but when I import it into Keyshot, everything from the 3D model is missing.

I think it’s because solids and surfaces are mixed but I don’t know how to fix it.