Image for Custom Header Issue

I am utilizing the Simplify theme for a client’s site I am working on and would like to use an image for the header bottom. I have put in the url but it is not showing up correctly. There should be a green and blue stripe across the bottom.

/* Header Bottom Color */
#header-bottom{background: url(https://griggs-es.com/wp-content/uploads/2014/03/LowerHeaderthin.png) no-repeat scroll center top #3c4143;}

The blog I need help with is https://www.griggs-es.com

Any help is appreciated.