Why Isn't the Background Changing?

I recently installed the Elegant InStyle theme on my site.

I modified the background image here’s a screenshot

But as you can see here, the new image only shows up for a split second while the default background image that was already there fades and comes back.

Here, you can see that it shows that the background is implemented in my Dashboard Appearance -> Background modifier.

What do I need to do to make the image I uploaded show up in the background permanently?

I’ve played around with some of the options on the Manage Themes page, but nothing seems to make this work as I would like it to.

What am I doing wrong? Thanks.

By the way, I ran across an old post on the forum here that seemed to be somewhat related, but I couldn’t figure out how to fix the issue. I read in that post that the background needs to be made transparent or something, maybe?

If that’s the issue, how do I make the current background transparent?