Vray model failed to convert to usd using connector.Issac could not open it

when I change another model ,it seems the same problem. Only part of Vray mtl could be converted to mdl mtl.
So how could I use some big scene model in the Issac env? Is there other way to connect without connetcor?Such as fbx or obj model with Vray mtl could be imported to Issac?

This is the comparison between original 3dsmax model and converted Issac model.