I shot footage yesterday and it played back great. I shot footage today and when I download footage to my iMac I get this message "QuickTime Player can't open "DJI_0004.mov".

What did I do wrong? The still photos look great but the video won't play. Can I slavage the footage or am I SOL?

Thank you,
mbenatar

Get another video playback program.
Do they make VLC for Apple devices?

Hello mbenatar, do you try to play back the video with other players? Do other videos work well?

Perhaps you turned off the aircraft before then camera had finished writing the video to the card.  Try re-inserting the SD card & powering up the aircraft for a couple of minutes.  If there's any part of the file missing, it should be added from the cache in the aircraft.