Hi,
The Parts shader has taken over from the Multi shader. It allows more than 16 textures. Normally the Parts shader internal network would be full of Object part and Default shader pairs, one for each material. However in this case the OBJ reader couldn't find the mtl file for the object for some reason, and the mtl file is where the materials are stored. Without the mtl file it couldn't created the Object part and Default shaders which normally be inside the Parts shader.
Does your object have a mtl file?
Regards,
Jo