Videos not working on the Unity Forums

What browser are you using (No I do not have this behaviour)?

Try copying the video url and watching the video over youtube and of course try a different browser, because like Benproductions1 the videos are working fine for me in my browser.

Please provide us with what browser you are using, have you also tried clearing your cache. Check if any plugins may be conflicting with embedded videos. We are not aware of this to be a widespread problem.

I use Google Chrome. I have cleared my catch. The only plugin I have is Adblock, and it has never interfered before.

@marry_christmas I don't want to watch it on YouTube but I am being forced to, that is why I want to find a solution.

Well it's important to know whether the video will play when you watch it over youtube directly.
I agree with Aurore this seems like a problem most likely caused by an add on - try disabling it.
You can also try right clicking on the forum page just above the video and selecting "inspect". Then navigate to the iframe element and make sure it's correct:

bryaslak's answer may be helpful: http://productforums.google.com/forum/#!topic/chrome/gfyOlHeTVuE