Why is my Divx not working?!?

I downloaded it like 3 times and it still won't work. Like when i want to watch the videos on instagram all it shows is a picture but it doesn't move, and you can also hear the sound of what's happening but you don't see the video.
It also happens to my vine like it completely froze, i can't hear anything or see anything.

I use firefox btw

Thanks for helping!