I’ve been testing the new Mac OS Monterey for couple of months now and since then, noticed the Brave Ads stopped showing.
But then, I noticed even other notifications were not showing up, like Outlook new received messages.
What happens is that the new Mac OS Monterey has a feature called Focus, to prevent distractions while you are working.
So, even though you have allowed notifications from certain apps, there is another thing you need to check.
If you use multiple monitors with an adapter that does some sort of screen sharing, make sure to check the box below to allow notifications when the screen is being mirrored or shared.
Even have mentioned this in the tweet below to Brendan. https://twitter.com/LuizLucena77/status/1439981376065966080
Hope that helps!