I recently upgraded to dropbox beta V187.4.5691 on my MacBook. I successfully backed up an external USB thumb drive to DB - meaning DB recognized the external device and asked if I wanted to back up. Now I want to backup an external hard drive - formatted as MAC OS extended (journaled)- and although it is recognized on my computer, it does not appear when I click I click preferences, backups, manage backups. How can I get dropbox to recognize the external hard drive in order to back it up?