My lab is 10.4. My laptop is 10.4. Students at various versions. I post a map package from my laptop at 10.3 to share with class. The students download from group only to be provided with empty map .. the data downloads and extracts to default folder (setting at ArcGIS Map Options > Sharing Tab) .. they can then select file menu in ArcMAP > then open and browse to the user folders to open project. I installed 10.4 from my laptop thinking it would resolve the issue and same problem. It therefore seems to be an issue with 10.4?
(P.S> another issue also still remains .. the folder name extracted from the package is a mile long ... issue with Spatial Analysis)