I've had the same problem. I ended up going back a version so it works again. I've been finding that obj. files come in as clay models so no good. Fbx. files (which are not supposed to be supported show and work). saying that when I try to export a render the fbx files don't show. Seems a bit all over the place at the moment. Bit of a lucky dip as to what works 1 minute and doesn't the next.