Configure your device settings before making in-app purchases and make sure they are enabled:
Amazon Appstore → Menu → Settings → In-App Purchasing → Tap 'Allow In-App Purchases' checkbox if it's empty.
If you don't have a payment method set and a billing address defined in your Amazon account settings, you also won't be able to make purchases:
Go to https://www.amazon.com → Log in with your account → Select 'Account & Lists' in the upper right → Your Account → 1-Click Settings.
If you're seeing an error while making a purchase, please take a screenshot of it and send it to us.