New laptop doesn't recognize hard drives- old one does

I know this has been asked before, but the advice was for older models, so it wasn't super helpful. I got a new Macbook Pro about 2 weeks ago. I used my WDMyPassport external HD to transfer over some of my school files from my old Macbook Pro. I tried today to transfer over the rest of the files and the computer doesn't recognize the HD, on either USB port. I have a Seagate HD with some other files- the computer doesn't recognize that HD, either. Both HDs will light up and start whirring when plugged into the new computer; the computer just doesn't recognize them. Both HDs open just fine on my older Macbook. I have no idea what to do. Please help?