One of my apps won't allow me to make an in-app purchase but all my other apps will

I have several apps that I purchase in-app items from (extra lives, coins, etc...) I have one app that will only sporadically allow me to make in-app purchases. When it denies my request an error message appears advising me to contact the iTunes support store to complete the purchase. But 5 minutes later I can successfully make an in-app purchase on a different app so I know there is no issue with my payment method. How can I fix this problem?