Backing up a show on a thumb drive

Hi!
I am trying to back up a show from a road hog 4 on a usb flash drive but the console doesn't seem to see it. The flash drive works fine, I am thinking that the problem has to do with formatting it specifically for Hog system. But I can't find any information about that in the user manual and neither in discussions or forums. Anyone has an idea?
Cheers!