Are you still having issues? If you are, please update your post with your Brave version and OS. This information can be located at brave://version.
You can backup your Rewards. See the information below.
Source: can i create bats backup? - #4 by CerealLover
Note: Consider backing up entire Brave-Browser folder too and not just User Data folder.
You can also try to update Brave using the installer. Per Mattches (Brave support), this should not impact your data: Why Brave is not updating anymore? - #2 by Mattches. Make sure you backup your Rewards using the information above and if for some reason you do lose data, you can reinstall from your backup.
Here is another post that may help you troubleshoot your issue:
Not receiving Brave ads fix it fast - #2 by CerealLover