I export as *.alx and name the theme something distinct. I load it in DM 5.0 using the Application Loader and it shows on the phone every time. Maybe make sure you are not exporting as the name of an existing theme.. that you are exporting as 4.7 OS (which makes me wonder whether all themes will need to be updated for 5.0 OS)... make sure you are loading it up properly in DM too.