Aquila said:
I already changed this setting
https://www.youtube.com/watch?v=RUbpu0eOVfY
and it worked for a while but now it doesn’t
It may not be your browser’s fault – YouTube make minor changes to their interface quite frequently, primarily to discourage people from downloading videos. When those changes happen browsers also need to be updated. Of course, the people who write YouTube downloaders soon update their software, too, so it’s all a bit silly.
FWIW, I often use a Python program youtube-dl to download YouTube clips (and some other videos) via the command line. It has a simple option to update itself and it tends to be pretty good at keeping up with YouTube changes.