Sometimes when you buy Coins / Diamonds, they do not immediately appear in your account. The transaction process usually takes seconds to a few minutes, but in cases of credit cards can last up to 24 hours for security reasons.
If the purchased Coins / Diamonds are not added to your account, try to delete the Cache memory of your browser and click to refresh the application. Instructions for erasing the Cache memory can be found here.
If the problem persists, please contact us and say precisely the day/time of the transaction and the payment method selected. If the transaction took place via Facebook, iOS, or Google Play it would be better if you refer to their corresponding support pages.