I just tried it, and it's working fine. You just have to make sure you paste the video in the "search bar" like this:
https://www.youtube.com/watch?v=2ylKlt0qkWo
You can also use it's sister-site
snipmp3.com, which deals with only mp3s.
If you're still having problems with it... it might be blocked by your ISP. *shrug*