If you are using the Firefox browser and not seeing a video, or having any video play issues or problems while using the Firefox browser...
Firefox has known issues using Flash and Java. We recommend watching CC videos on another browser like Chrome.
Test playing a video with the latest version of Chrome to see if you have the same issue? If the video plays properly on Chrome, you will know it is a problem with Firefox.
If you would like to use Firefox, you may try fixing the issue with your version of Firefox.
First, check and make sure you are using the latest version of Firefox and not an older version.
Next, check that Java, and Flash are installed and up to date within Firefox?