Replying to "Error loading player: No playable sources found"

Need some help. So I tried uploading a video to NS.

It took an hour or so to upload a 123 MB file. Not sure if that is part of the problem.

Anyway after uploading, in the pop up window, there is 'Tag your media' and I presume u click that to see your video.

So I did and I got "Error loading player: No playable sources found".

What does this mean? Please help.

I want to post this edit, but I don't want to spam it multiple times.

Thanks guys