Assembly wont load my .stp files regardless of how I save it. I could be making some basic mistake

So far i've tried changing the Import settings, Disable ‘Enable 3D Interconnect, ‘Import multiple bodies as parts, and Turn on the ‘FeatureWorks’ add-in. Nothing seems to work. I've tried manually referencing the files, and it seems to know where the files are located but does not load them anyway.