in advanced settings you can reset Brave settings. first it worked for me, but after a little while youtube started to show ads again 
if Brave doesnât block youtube ads anymore then you should install add blocker.
here is awesome add blocker âAddblock plusâ. it works also with Brave browser.
Iâm not sure does it block Brave rewards ads, but I donât care about Brave rewards anywayâŚ