I’m sorry you are having trouble with embedding on your website. The difference is that the university website where you embedded successfully the iframe (the first link) is likely a wordpress.org website, i.e the university is hosting the website itself. On the other hand, your own website (the second link) is a wordpress.com website, which means it is hosted by wordpress itself. The problem is that embedding on wordpress.com is only allowed for a small list of whitelisted websites (for example youtube) that is manually decided by Wordpress itself.
A few users have had this problem, and we are started to look at what we should do to get whitelisted, but it might be difficult in any case. On the technical side, the first step would be to become oEmbed compliant (not too hard), but ultimately the decision will be at the discretion of Wordpress only. We are also looking at existing plugins (potentially not free) that would allow to do this. We will keep you updated about this issue.