See, I have nice model in blender.
But when I export with default settings to USD, I do not get any materials:
Also, check this out it kinda empty:
How to start finding where the problem is?
I would need to see the material graph to answer - but if for example the material is layered then it would not be able to handle the conversion.
There are UMM material templates that would make it work a lot better: Blender — Omniverse Connect documentation