Thank you both, I am letting the dev have a look.
@derekflood, it is a case of not supporting yet that way of describing the Material. The NodeGraph definition needs to be supported. We created a ticket for that
@201010, your file is not using MaterialX but MDL render context.
That is not supported with Interchange. Also, I get error and failed import when trying to import with USD Legacy.
Could you export your USD using another render context than MDL?