I imported a new set of .mov files into a project. They imported just fine and show in my preview window just fine. Upon export, all of the clips from that imported batch do not show in the exported video. Audio from those clips work fine, but no video. I then opened the project on a mobile device and those same clips don't show in preview when editing. Just black screen. What can I preview on my desktop but not my phone? Why can I import a file, preview and edit, but have the export of that clip only be the audio?