Transparent objects usually mean Maya knows it has a material and which material. Just not how to display them.
So a UV map will be required. Automatic mapping should give a starting point for test purposes.

The first thing to do is go odd normal hunting, fastest way by turning off Two Sided lighting. I do get one or two odd faces
on imported models, and if using obj I expect some faces to be inverted and locked.

Scroll down to my reply in this thread:
https://forum.simplymaya.com/showthre...threadid=27049

Cool importer: Masilo. Opens .sib/.sia files in Maya. Lovely.
https://animatic.no-ip.com/cgi-bin/silo-wiki/index.cgi?


I've tried to recreate your problem and the grid plugged into color attr shows up just fine here on my imported silo model.