We are so sorry to hear that you have problems playing the videos.
One thing that helps us solve the problem: When you (try to) play the video, could you right click on the video? You should see a "report a problem" option. Please click that and submit the problem - With that, we will receive more information about your specific situation and can try to really solve the issue.
Here are some reasons why you might be having these issues:
1. Check your Internet Speed
The most common cause of this problem is that your Internet connection speed is not fast enough to support video playback reliably. While we take many steps to optimize the playback experience for each viewer, there are some minimum requirements for a smooth playback experience. If you want to check your internet speed you can go to: http://www.speedtest.net
2. Try a Different Browser
Sometimes different browsers can cause problems. If you're using Internet Explorer and your video doesn't play, but things are looking great in Chrome, please let us know! Our website is optimized for being viewed with Safari, Chrome or Firefox browsers.
3. Clear your Cache
It may seem silly, but it's an amazing fix in a number of situations. Try clearing your browser's cache and restarting your web browser. Click here to learn how to do this in several different browsers.
If you face further difficulties, please contact our team at firstname.lastname@example.org .