Restore course backup file attached videojs_samples.mbz . (Note: You might need to increase the max upload file size on the site/server) Make sure videojs is enabled and on the first place, youtube, flash support, RTMP streams are checked. View the restored course on different browsers (including mobile) make sure you can play all videos/audios. In "html5 embed" you should be able to show captions and jump to chapters.  (The media links added within a label should be embedded and able to be played in the course page, while to test media links added within other resources or activities you will need to access the activity).  Change interface language to one of  this list   make sure the video player buttons are also translated (enough to check in one browser).