I got it working finally.
Make a backup of your bookmarks, and the Brave settings (on mac /Applications/Brave Software)
Then go to brave://flags, enable sync, and relaunch. If it crashes and can’t launch, remove brave and Brave Software folder in Applications and reinstall.
Then enable sync on the new install, and set it all back up again.
I was pretty frustrated, but happy it is back to normal now.