Gotcha. At least you figured it out and it was simple.
Create a Show for Smackdown and set it to use that arena. This was a change they made last year so if you didn't play it (don't know if you did), you might not know. Arenas can't be selected as they used to be. Now you set up the Show and select the matchup graphics and backgrounds to round out the presentation. That's what this sounds like. Once you do it and see the process, it's pretty easy.