BG Image Not Showing Up on Firefox

Hi there, I am using the mandigo theme and I have added a custom background image. It shows up on explorer as it should but it wont show up on firefox and a number of other browsers. I thought maybe I screwed something up so I tried starting from scratch by downloading the most recent version of the theme and starting over, but no, the same thing. Can anyone tell me what I’m doing wrong? My site is at https://www.watercarsolution.com