I have this exact same problem. Both me and my friend have the files physically on our harddrive, he has it in his editor aswell.
I can see the files in the perfoce server depot also, i can force download them (Get revision), but still they dont show up in editor but appear in windows explorer locally. All files are .uasset files and straight from him (working) and both of us has fresh UE downloads and blueprints only… We have worked back and forth then after an hour or so, this happens.