Whenever I try to play a video in full screen, it does nothing. I press the button, it flashes as if the video disappears, and then returns to how it was before. I have successfully gotten into full screen, but I do have to click the button a thousand times until it takes effect. And there is no surefire way that it will go into full screen, no matter how many times I click the button, it's generally random. I have tried this on multiple sites, and it is all the same. However, I have yet to try it on a video that is not on the internet. This is a new installation of Ubuntu, I have installed it before, several times, and never had a problem until the newest installation. I remember, whenever I used to go into full screen video, there being some sort of program running that had no relation to anything else.
Perhaps you could go into a full screen video and tell me what is running so I can install whatever I'm missing.