Gameboid Emulater Purchased But Not Installing

When I click my apps it shows gameboid emulater as purchased. But when i click to install it, it sppears to install at first but then just goes back to saying purchased. How do i fix this.

Also I use a prepaid credit card to download my apps. I think it might have been close to zero when I bought the GBA Emulater. If this was the case would it say purchased even though I never paid enough money. I tried restarting my phone and clearing my app cache.

Okay I think I realized my prepaid credit card didnt have enough money on it. However now I cant even download it with another credit card because it just keeps saying purchased. Is there some way I can unpurchase it then redownload using another credit card? I don't see a refund button either.