Generally, this is a user issue.
Here is the obvious stuff to try...
Try downloading again to your computer/device.
If you can, download to a different computer device.
Then, try playing with a different video player other than your default player.
I'm purposely avoiding changing any settings on your player(s)...
If you're still not able to view the video, the mp4 file could be corrupt at PM. This is rare, but it has happened in the past.
If these suggestions are not successful, don't hesitate to contact PM customer service directly on Monday...they'll get you all good to go.