html embedding video

Hey, I'm a student helping to implement the elgg software at a university. I've been trying to embed videos into pages and was wondering if anyone could tell me why when I go into the edit page, open the html editing box, paste the embed code, update it, the video comes up in the description box of the edit page, and when I save the video doesn't show up?

Long-winded question I know. I've attempted to embed a video in this page below to see if it'll work on this software. if so, you may have already solved the problem we're having. Any help is much appreciated! =)

New HvZ Trailer from HvZ Source on Vimeo.