Recently I saw that some people had this problem not getting Brave ads after getting a new PC and installing Brave. Apparently the fix to this for most of them was just to force a first notification using a tool like this one. (It was my case)
So I was thinking, maybe it could be a great idea that when you enable Brave Rewards for the first time (action), it shows a test notification saying “hey, this is what it will look like when you get an ad!” (reaction), similar to what we get on mobile if I remember well. This way it would also prevent the problem I was raising above.