Well I guess jewtube decided to roll out anti adblock messages before watching videos. I just got my first message saying "youtube does not allow ad blocking software".
God forbid I want to watch something and not have my eyes and ears assaulted by Pfizer/McDonalds/Disney/etc. at max volume.
If they actually ban adblock I'll just stop using it entirely. It's not usable without it, and it's not worth the hassle to get around it.
Youtube has been testing this kind of thing over the past few months. I haven't gotten hit by it yet but if you have with an adblocker, chances are it's a direct message telling you to unblock. Updating uBlock should work as a temp solution.
You should be using Youtube Enchancer and Sponsor Block too.