Generally, videos do not display correctly on TED-Ed lesson pages for one of two reasons:
First, all videos on ed.ted.com are currently embedded from YouTube, so if you are accessing ed.ted.com from a network where YouTube is blocked, you’ll see a blank white space where the video should be.
If this happens, we suggest that you reach out to whoever administers your school's IT systems to see if you can whitelist videos that are embedded on ed.ted.com
Second, if a video that a TED-Ed lesson is based on has either been removed from YouTube, been marked as private by its uploader, or had embedding disabled, then we are no longer able to display that video on ed.ted.com. In any of these cases, you’ll see an error message in the YouTube video player indicating why the video is not available.
If this happens, we suggest that you reach out to whoever created the lesson page to notify them that the video is missing. If you are the author of a lesson where the video is no longer available, learn how to add a new video to your lesson!