The products you are trying to purchase in the game are sold through the Google Playstore or the App Store and as different players have different payment methods, there may be multiple causes of problems.
How to resolve payment failures:
If the problem is due your payment method / payment provider, please contact the payment company (PayPal, credit card issuer, bank, etc).
If the issue has to to with a micropayment payment limit, you can check your limit by contacting customer service of your payment company.