Some tips I've used running this myself...
On first install, or update, you can run the add-on manually via the Admin -> Tools -> Cron Entries -> ForumBackup link.
After running manually and no errors appear, check your backup directory, and make sure that the backup files exist. The addon will verify that the backup files are created, readable, and that they are not 0 length, but it's good to double check at least after the first install. If all else fails, turn on debug and send me the contents in a conversation.
If you run more than one backup a day, make sure to update the
Date Format so that it includes the time, otherwise the backup file will just rewrite the existing backup each time it runs that day. Adding
His to the date format will include the hour, minute, and second that the file was created. See this link for more date formats examples:
http://php.net/manual/en/function.date.php.
Normally, you'd probably want to set the backup file name once, and keep it, but you can change it if you need to. The filename option currently only accepts alphnumeric characters. The addon will still only keep the number of backups you specify for the database and forum, no matter what the name of the backup is.