I found that most of my problems of this nature occur because of a faulty Micro-USB cord. CHEAP generally equals USELESS when it comes to these cords. Before you get completely frustrated, try using a high quality Micro-USB. I have been given brand new cheap ones that have no connectivity whatsoever. You might also try a different USB port on your computer, or a different computer entirely.
I am betting that it’s your Micro-USB at the root of your troubles…