Fun but I’m having a technical difficulty – QuizUp® Review

I love this game so much, there’s so many different categories which helps it cater to everyone, but it won’t let me buy the ad free thingy. It’s giving me something saying it’s not valid or whatever, it’s never done this to me before and I have enough iTunes credits. If a developer could help me out I’d appreciate it.
Review by e.marie.112 on QuizUp®.