Looks like you’ve already tried a lot. Until someone replies who might actually have a clue, I’m just going to fish in the dark here:
Could you try HERE if notifications from your browser can come through at all? First click on “Authorize”, then “Allow” in the appeared Popup and finally “Show”.
Do you get a notification? After doing that, Brave could possibly show up in the Windows notification settings as well.
When you reinstalled Brave, did you do a “hard” removal, meaning also removing user-data in the AppData folder? (This will of course remove everything, so only do that if you have nothing to loose in Brave)
You probably have read about this, too, but do you use a VPN?
Is the reagion/locale of Windows set to English (USA)?
Hopefully we’re lucky and one of those things helps 