If you make purchases in other apps without any problems, this can happen due to one of the following reasons:

1. A problem with the internet connection. Your connection must be stable to process purchases, so we recommend using Wi-Fi or 3G/4G connection.
2. Temporary problems with the app store. All in-game purchases are processed by the application stores where the game was downloaded from, so there is a chance the store is temporary unable to process your request. In that case, just wait several hours and try again.
3. Some problems with the app. It can be solved by restarting your device.

If you've never made purchases in any applications, the problem can be caused by one of the following reasons:

1. Incorrect payment information. The easiest way to fix that is to delete the payment method and add it again (or a different one).
2. Unsupported payment method. The payment method you want to use might not be supported by the application store. The list of available payment methods can be found in the corresponding sections of the Apple and Google websites.

If you're still having problems making purchases, please contact the customer support of your application store.