If you've made purchases in the game or other applications before:
1. Your internet connection. It has to be stable in order to make purchases, so we recommend using Wi-Fi or at least a 3G/4G connection while making purchases.
2. Temporary problems with the app store. All in-game purchases are processed by the store where the game was downloaded from. There is a chance that the store is overloaded and unable to process your request. In that case just wait several minutes and try again.
3. Problems with the store app. These are usually solved by restarting your device.
If you've never made purchases in the game or other applications:
1. Incorrect payment information. If you made a mistake while entering your payment information, cancel the payment and start over.
2. Unsupported payment method. It may be that the payment method you want to use is not supported by the app store. The list of available payment methods can be found in the respective section of the Google website.
If you're still having problems making purchases, please contact the app store customer support.