''duplicate of https://support.mozilla.org/en-US/questions/1132397 - locking'' I try it when turned of all the add-ons. 1. Open the page with the video. play/pause button is already showing that the video should play, but it does not play. 2. If you click on a video, then the play/pause button will pause, and the video still will not play. 3. If you again click on a video, the play/pause button to switch to Playback mode, but the video still will not play. then 2,3,2,3... and the video still will not play. 1. Open the page with the video. the play/pause button is already showing that the video should play, but it does not play. 2. If you click on the play/pause button, then the play/pause button will pause, and the video still will not play. 3. If more time to click on the play/pause button, the button to switch to Playback mode, and the video will start to play. I want to have in the first paragraph the video playing as well as shows the play/pause button.