Linda, I can only think of two things. First, make sure you have downloaded Adobe Flash Player, type into your browser (adobe flash player download). Second would be to make sure what browser you are using sometimes Google Chrome has issues playing some flash files, try another browser, IE or Firefox. Also before I do anything, try closing the computer and reboot. Sometimes if you are getting a lot of updates you may not have the resources to run video.
Hope some of this help, there are deeper issues also that I do not cover here possible