A:Answer I would 1st verify that the USB cable you're using is a known working DATA Cable.
That test can done by successfully transferring data to / from another device, like your cell phone.
If you've using one of those cheaper USB cables you find at the check-out lines at the grocery store, it may be just a charge-only USB cable. A charge-only cable has only 2 internal wires, compared to a data/charge cable which has 4. (2 for power, 2 for data sync). Note, lust looking at the end connectors is not a sure way to tell.
Hope that helps.