I don’t understand it, but going through various githubs, the problem has been discovered. Here it is:
YouTube changed their code to make it more difficult to extract the throttling parameter decryption function.
There was some coding demonstrating the problem but it was way over my head. Hopefully fixes are coming soon as the issue was marked as urgent. It looks like they know what needs changing.
I think I’ve just found my next watch. It looks more useful than my current Fitbit Versa. Thank you for bringing it to my attention.