Responsive theme but background image not resizing??

Hello,

I haven’t built a site in years and have to finish a wordpress site ASAP for a small business. While I don’t expect anyone to be familiar with the theme I’m using it is from Themeforest, it’s called Jupiter. Here is the link: http://themeforest.net/item/jupiter-multipurpose-responsive-theme/5177775

Here’s my problem. I have a background image that is not auto resizing as I adjust the size of the browser. It looks terrible on mobile devices. The demo of the site auto adjusts, it is a responsive theme. I’ve looked over all the settings, and there are many, in the control panel. I just can’t figure it out. Anyone have any suggestions? I’ve posted this question in the theme forum but no replies as of yet. I’d appreciate any input. Thank you!

PS the theme is advanced and has many settings, I’m hoping to be pointed to where to look and what to change versus going into the CSS files etc..