Suddenly Stops Playig Music From Docked Device.

I received my Jensen JiMS-210 as a gift about a year and half ago. I have been using it as a docking station for my iPhone, and enjoying the ability to play my music from my iPhone. One day, the Jensen stopped playing through my iPhone. The music progresses, but no sound comes out of Jensen. Sound does come out of my phone when it is not docked. Also, the volume button disappears now when docked. I tried my husband's iPhone to see if it were a problem with my phone or Jensen. My husband's phone doesn't play when docked, either. What happened? I used to be able to dock and play through my phone with no problem.