Adding an OBJ with colours and textures to GrabCAD

I'm trying to upload a sculpted file done in Blender which has colour and textures to GrabCAD for the purposes to get in colour printed on something like a Stratsys J55. It already exists as an OBJ with the MTL colour and texture files. When I upload them to 3D Viewer on GrabCAD I can only see the in greyscale version. I think I have tried all the export versions out of Blender. It's always the same.

Any help would be greatly appreciated.