On occasion, Amazon will restrict customer information from being sent via their API. In order to remedy this issue, you'll need to submit a support ticket to Amazon directly from your account to regain access to customer data.
Amazon will arbitrarily remove access to the following:
AddressType, AddressLine1, AddressLine2, AddressLine3, BuyerName, Phone, PurchaseOrderNumber, RecipientName.
It is their opinion that this information is not needed if you ship most of your goods through FBA anyhow. They are also slowly restricting access to customer information for prominent sellers.
To request that your access be adjusted to allow the additional information to be sent via the API, see this link:
Note items 10, 11 and 12 in the link above. You will need to submit the appeal to Amazon via your own Amazon Seller Central account. You can do this by logging in to https://sellercentral.amazon.com/ and going to the "Help" link at the top right.
Once you're there be sure to press Get Support to submit your request.