Earlier this year, Youtube started blocking a lot of Tor nodes. I think they're throttling instead of blacklisting, and this allows for a workaround: you pick "New Tor circuit for this Site" from the main menu. However, since the error message brought you to google.com, that would change the circuit for that domain, not for youtube.com. The trick was to hit the back button (or open youtube.com in a new tab), and then change the circuit. This worked, because blocked nodes are only redirected when they access a video directly (but not on the homepage, a channel's page, etc.).
Since a month or so ago, blocked nodes are redirected regardless of the landing page, and the method always redirects you for google.com. Here are a couple of remaining options:
- Go to one of your previously loaded Youtube tabs, from before the node got throttled, and choose the option from there. You can now access Youtube again in all your tabs.
- Start Tor as a service from the CLI, and use
mpv '[URL]' or
youtube-dl '[URL]'. The daemon uses a different circuit. If that's blocked, use
killall -HUP tor (which changes the circuit) and try it again.
- Replace 'youtube.com' in the URL with 'invidious.snopyta.org' and view it there.
- Close Tor Browser and reopen it.
- Wait 30 minutes to see if it has unthrottled.