Aperture: "Please Try Again Later" message when ordering books or prints
When you place an order for books or prints within Aperture, a dialog "Please Try Again Later" might appear.
This can occur if you've set your Apple ID to use two-step verification instead of security questions. For more information about two-step verification, please see Apple ID: Frequently asked questions about two-step verification for Apple ID.
To resolve the issue, change your Apple ID to use security question verification. Apple ID: Turning off two-step verification for your Apple ID explains how to do so.