I finally managed to recover my old Brave wallet with the 16-word passphrase. I was able to put in the old passphrase once my first BAT payment was made from using the browser over the month.
When I recovered the old wallet, it combined my monthly earnings with the old funds, which I was very happy with. However, since then, the browser has stopped sending me ads. I used to get maybe 4-5 per day.
I have checked all the obvious issues.
Has anyone experienced this before? Any idea how to resolve this issue?