Why is the registration address of an eBay user/buyer empty or null?
Answer
Summary
Why is the registration address of an eBay user/buyer empty or null?
Detailed Description
eBay always returns complete RegistrationAddress details (including Phone) when you retrieve your own user data. RegistrationAddress for another user (except for Phone) is only returned if you have an order relationship with that user AND that user is registered on DE/AT/CH, regardless of your registration site and the site to which you send the request.
So unless the buyer/user is registered on those sites you will not be able to get back registration address.