I updated ublock but it didn't stop the ads, so I can see others doing the same. I'm guessing it didn't actually pull the very latest version or the very latest block lists for whatever reason, but others might be less patient than me.
Make sure you have no other adblockers, disable enhanced tracking protection for youtube (shield icon at address bar) and make sure you have no other custom rules set for youtube.
Also you don't need to update all the filters. Just the quick fixes section -> click the clock icon and then update.
Also this all assumes you mean uBlock Origin, not just uBlock.
didn't work for me at first too, but other YouTube specific ad blockers had side effects (videos opened in new tabs would play automatically instead of waiting for you to switch to that tab, etc)
here's what I did:
reset uBlock to default settings, then purge caches and update
clear all caches in your browser (in Firefox/Chrome you can just search for cache in the settings search bar and it'll come up)
I think it's meant for people who currently use ABP, uBlock, or one of the other countless bad ones as opposed to the far superior uBlock Origin, or Adnauseam.