hello. My name is***** can help you with your question.
this will default to the returned data settings in the PayPal account only if it's not set by the request. normally this would be sent with the request..
The notify URL applies only to DoExpressCheckoutPayment. This value is ignored when set in SetExpressCheckout or GetExpressCheckoutDetails.
IPN should be used to verify the order was correctly handled by PayPal, however, you still need the return url to show to the user
Auto return is a separate setting.
and is that what appears to not be working? Because it sounds like it is going to the IPN page. in the IPN page is just your own page to tell you that the transactions gone through where the return URL is the one that the customer will see. Here is additional information that deals with setting the return URL. Keep in mind that information you've seen or information I've given you may be depreciated because they do change the API frequently so this will give you the most current information on the return URL and its requirements.