Just to explain the youtu.be thing - YouTube introduced this kind of web address to make the links shorter. Here are examples of the two different addresses:
https://www.youtube.com/watch?v=orph2wkLFbI
https://youtu.be/orph2wkLFbI
Notice how in the second one the following is missing: /com/watch?v=
It's to make links shorter for sharing them on Twitter etc where you have a limited character count, and I guess it makes the link look a bit neater as well.
Maybe our form doesn't like the youtu.be links - Jordyboy, can you try entering the first link above into the form?
Both types of link are available to copy and paste from YouTube. The one you should try using on AB is the one at the very top of the screen in the address bar. The other one which doesn't appear to work on AB (I'll test it in a sec) is the one you get when you click the share button underneath the video. Hopefully that all makes sense, I've attached a video to this post so hopefully it will work!