Used this add-on for a long time and it's been great but recently I reinstalled it on my browser and it seemed it no longer worked on embedded videos. Eventually I discovered that when the dialogue window to save the file fails to open, it's possible to click a blue button at the top of the download page which will be labelled 'Download 1080p' or whatever quality you've chosen. Then the dialogue window appears allowing you to save the file. It's not totally obvious though and I only figured this by chance, having never needed to do it previously. But ultimately the add-on works so that's the main thing!