Unable to add images in Upfront

Hello,

I've been working on a website using Upfront with the Fixer theme.
When I try to select an image for a background, nothing happens. It doesn't seem to matter if it's a single image or if I try to add to a slide. Also, I tried to use Spirit and got the same result leading me to believe the problem is with Upfront.
I am able to upload images to my gallery, and I can drag and drop the "add image" place holder from the side menu, but I just cannot actually add an image to the background or to the page itself.