If you successfully made a purchase through the App Store and your coins were not added to your balance, something you could try which usually works is to completely close out the app and then reload it.
Sometimes it can take a bit longer for the iTunes servers to sync up with our own, and this restarting of the app a couple of times can jump start that process.

If you have tried this and your coins are still not reflected in your balance, please contact us so we can manually add your purchased coins.
It will also be greatly appreciated if you could provide the iTunes purchase receipt when contacting the Support team.