When you say that it loads in the preview but it doesn't allow you to save, are you getting an error message or text to say why you cannot publish the page?
Yes. Since it's ment for video - when saving it tells me that my ebedd code doesn't mean to regular expression for YouTube or Vimeo basically. So it seems like at publish time HS checks wether it's a YouTube or video URL and if not it refuses to save. you can see below. It shows the preview of sketchfab - but refuses to save it