If the error says something like "this transaction has failed for the following reason..." then it is a message returned by your merchant provider.

Seems like some setting in your merchant account is expecting to get the ship to information.  

We send the ship to information when you've check-marked to activate physical fulfillment, but otherwise we don't populate shipping fields that get sent to your merchant provider, so as not to confuse buyers when they get the receipt w/shipping address info in it. 

So it could be something in your merchant account you can turn off.

Keywords: shipment, shipping