Can't buy starter arena

I may have misunderstood but I thought I could buy the 17x6×1 arena after its been placed originally, to place another in a build of my own. If I've misunderstood, please lmk. If not, it doesnt seem to be working. I get an action bar notification that says the arena is already placed in the world. I tried to delete the arena at the arena and reattempt, but got the same outcome.