Video file format won't play
I just downloaded the clip from provided Dropbox link and found that the file is repairable. Please try to diagnose it using MP4repair.org or in case you're on a Mac computer using Treasured. You will be able to repair it in a few minutes.

Regards,
Javier

(As crew of Aero Quartet I may receive some form of compensation, financial or otherwise, from my recommendation or link.)