If you’ve made in-game purchases before:
Check your internet connection. It should be stable, preferably Wi-Fi or at least 3G/4G.
The store may be temporarily overloaded. Wait a few minutes and try again.
App store glitch. Restart your device - this often helps. If this is your first purchase:
Incorrect payment details. Remove and re-add your payment method.
Payment method. It may not be supported - try a different one.
Important: All payments are processed by the app store from which you downloaded the game. If the purchase still fails after these steps, contact the app store’s support team - they have the necessary data to assist you.