Some external drives do not draw enough power from the motherboard to make them work without one of those USB cables you plug into two USBs on your computer and the other side into your drive. It may be this.
Has the same drive worked on this computer with another operating system installed. If not this may be it. You can get these cables at most electronics stores.
If the drive HAS worked on the computer with another operating system.....it will be something else.
Please try other USB ports if you have not tried that already.