Studio theme - child.css header-wrapper style doesn't change display

Studio theme,
I'm trying to add a background image to the header. By header I mean the section where the buttons and logo are located. An element inspection shows that to be the #header-wrapper div element.
I've modified the #header-wrapper statement and put it in the /studio-child/_inc/css/child.css file and I see no change. It appears the "custom styling" for the header overrides the css styling. I tried leaving the header color blank but it just puts the default black color for the header.
fyi here is the statement I put in the child.css file:
#header-wrapper {
background: #ae2f27 url(images/header_back.png) no-repeat;
}

yes, I also uploaded an image to the images folder in _inc/css/

any help?
thanks