First, can you see a video directly on Youtube? Can you see the video on this page?:
https://www.youtube.com/watch?v=j0-L-q14kQ8
Next, try a different browser. If you use Chrome try Safari (Mac) or Internet Explorer (PC). If you use Internet Explorer try Firefox. If it works in one browser not the other there is something in the malfunctioning browser that is blocking the Youtube feed.
Hopefully this will help isolate the problem.