Not being able to purchase coins could be related to many reasons.
- It is better to start by checking if there are any restrictions on the device. You can check your restriction options by going to Settings > Screen Time > Contact & Privacy Restrictions > iTunes & App Store Purchases > In-app Purchases. If you want to make a purchase, you should allow In-app Purchases on this screen.
For more information, you can check out the following link: Prevent in-app purchases from the App Store - Your internet connection should be stable in order to make a purchase. We suggest that you use Wi-Fi or at least a 3G/4G/LTE connection while purchasing any package.
- There might be temporary problems with the store where the game was downloaded from. All in-app purchases are made through the App Store and there is a chance that the store is not able to respond to in-app purchases. There might be temporary problems with the store. You can also restart your device and try again.
- Your payment information might be incorrect that’s why you are not able to complete in-app purchases.
There is a chance that the payment method you are using is not accepted by the store. To see available payment methods in stores: Available payment methods in App Store - If you are still unable to make a purchase, you can contact us and you can also contact Apple Customer Support. To contact Apple Customer Support, you can check out the following link: Contact Apple Support