Issue when importing FBX or OBJ files into a Scene

When I try to import trusted fbx's just as the one in https://docs.sumerian.amazonaws.com/tutorials/create/intermediate/interactive-terrain/ I just get the error "We couldn't import the fie. I may very well be corrupt. Grab another copy and try uploading again". I've tried other fbx and objs without success. Objs produce a different error about not finding the root ID, but I imported the same OBJ file yesterday without any issues.Can you help?