Possible solutions: invidious.io and piped.yt
I suspect that’s a growing pain. Same reason it happened on Lemmy, especially right after the reddit API changes.
Seems to me YT is just blocking the instances so they have to move their servers constantly. Big or small instances, both get blocked every few days. Thankfully there are enough instances, so you can always hop. But it does require more intervention than Invidious, which doesn’t proxy your requests to Google.