Not recognizing DiskGo Edge external harddrive??

My father just sent me a DiskGo Edge external harddrive (used by him but only for some email files, no damage I know of) and it is not at all recognized by my computer, won't show up in disk utility or anything- it also won't show on my school's computers which are also macs. I've tried thier website troubleshooting page and no luck there. It did work on a PC before. There are two blue lights on it, and altough two are on when the power outlet is plugged in, only one is on when i plug the USB in my macbook. It's clearly the external itself since it hasnt shown on 2 computers-- but how do I get it to be recognized??