It's a legally purchased App Store app and not a cracked version, right? There is a big difference between TomTom and MapQuest. One is paid because it has preloaded maps and doesn't require internet access. I'd want to get TomTom working if I paid for it.
If you bought it in the App Store, it should open fine. Try rebooting. If it still doesn't work, contact an iTunes specialist at Apple.