When you receive a rejection for your app by Apple which claims "Specifically, there was an error purchasing the In App Purchase", there is a problem with your Payment Mappings between your Apple In App Purchase Items and your PressMatrix edition.

Please validate and or fix the following configuration in your Apple iTunes Connect

1. Your In App Purchase Item has to be present for each issue you want to sell via In App Purchases
2. Your In App Purchase Item's status has to be "Waiting for Review", "In Review" or "Approved"

Please validate the following configuration within your Pegasus Publication

1. Each edition which has a price set (> 0) has to have a valid iTunes Connect Product ID (Please validate, that an In App Purchase Item with the exact same Product ID exists within you Apple iTunes Connect)
2. Each edition which has no price set (0) must not have a iTunes Connect Product ID associated with it