Uploading 2 textures to sketchfab

Hi all, I can upload models onto sketchfab but I’m having an issue. One texture is fine and uploads ok - I use the same texture on all sides. But, the problem arises when I try to upload 2 or more textures…everything goes black. I’ve tried everything to resolve this and the only way to do it is to split my models and put them on as separate.

Have a look at my sketchfab

Sketchfab - this is a simple shape and I would like to make the curves black but this happens:

Sketchfab

I’ve cleaned backface and my model is manifold with no stray parts.

As you can see from my other models, I’m having the same probs - any ideas???

Why don’t you upload the SketchUp file so we can take a look at it?

ud.skp (1.8 MB)

Sorry, and thanks!

Please people!!! I need help before I go completely crazy!