Sometimes a video decoder is needed. Since we can't see this video, no one could guess what decoder is needed. Tell them to upload it on Youtube and that usually forces them to encode it for all to see.
Bob
When using Facebook or some web sites not all videos work. Example YouTube is no problem but if a friend sends a video post I cannot always view the video and if I go to that web site I cannot view the video.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic