C7000v2 not detecting USB Drive

I have a C7000v2 Nighthawk and have been trying to use a Seagate external drive with it via the USB. The drive is on the compatible list and I've set it up exactly the way everything say to do. However it just doesn't show up in the list on Readyshare. I've tried unplugging and plugging the drive back in...rebooting the router. Nothing makes it detect the drive. Strangely a cheap Lexar thumb drive shows up when I try that but disappears randomly from the list. Any help would be much appreciated.