As a responsible computer user, I like to keep my machines protected. I recently acquired a surface pro 3 with win8.1 and activated windows defender. So far so good. BUT... defender will not/can not update. It insists there is no network connection. Yeah right. So my questions are, what is going on, what do i look for, and how can I resolve this issue? 

I would really prefer to use defender as an antivirus program, but if I can't work past this "connectivity" issue, I will have to go another route and try AVG or Avast or something similar, none of which I care for.