• There may be overload issues in the Google server. Please wait for a while, and try again. 
• If there is more than one Google account logged into your device, please check if the purchasing account has a properly registered payment method.
• If your payment method is a credit card, check your credit card company if there are any restrictions related to online purchases.
• Check if your information in your Google account is written the same as the information written in the payment method.

Massive Gaming Support Team
https://massivegaming.oqupie.com/portals/1828/inquiry