That happened on my wife's PC with ublock origin running FF but not on mine with a similar set up. I putzed around in ublock looking for a setting to fix it, gave up and disabled it overnight along with SponsorBlock for YouTube and decided to fix it in the morning.
In the morning I re-enabled the two and everything worked fine. I still don't know what happened or what I did but it's all working so all better.
Apparently Youtube are updating multiple times per day to get round the fixes by the uBlock guys.
Who wins?
Youtube with $$$ and high level engineering pros but possibly limited budget/timescale for the project.
Or adblock guys with years of experience getting round this stuff, maybe limited free time but also doing it for ideological reasons rather than pay.
Some suggestions that Youtube may be at least breaching EU law.
Adblock seems to be winning so far.
I had to turn it off for about a week & watch a bunch of ads trying to convince me to sign up to workshops to learn how to make money by convincing people to sign up to your workshops about how to make money but its back on now without any obvious issue since.