Purchase problems occur for a few different reasons, their fixes depending on device type.
Apple:
Because Apple processes payments made toward the game, it’s important to have your device settings properly configured before making a purchase.
If you’ve made an order that has been processing for 24 hours or more, please contact iTunes Support here.
If you are not waiting on a purchase, please check the iTunes in-app purchase restriction guide for further information.
Google Play:
If you are trying to make a purchase with your Google account, it’s possible for you to experience the issues mentioned above. In order to resolve these, please follow the link to Google Play Support.
Samsung Galaxy App:
If you’ve made an order that has been processing for 24 hours or more, please contact Samsung Support Here
Amazon Appstore:
If your order hasn’t arrived after 24 hours after you made the purchase, please contact Amazon support here