Dropbox sync is not happening. This is a bit of a monster of a site at 50 GB (32000+ images in the wp-uploads folder as it's a wallpaper site.) So I understand it might take a while but 6 hours should be more than enough time for the DB backup to show or any file at least.
I have just installed this plugin today so it is entirely possible I messed something up though with how simple it seems to add dropbox mirroring I'm unsure what I've done wrong.
I'll grant support access as soon as I submit this ticket. If support needs an admin account or ftp access just ask and ill set up accounts for you.