Resolved! I’m in the process of moving the site from Go Daddy to Media Temple. The problem did not exist there. I just wonder what it was about Go Daddy that was causing this?
I have done a complete reinstall and left out my child theme and plugins, but I still have the same problem. I have been searching for a few days but I have come up with nothing.
Adding the “!important” worked just fine for me. When I tried adding the function to my child theme it corrected the background, but also made my wp dashboard disappear.