the pp_confirm page will have 2 server behaviors on it:
-get payer profile
both will have the api credentials in it.
open the server behaviors panel to locate the server behaviors.
Make sure that you have accepted the billing agreement on paypal site for the api credentials.
if they are for a live account, make sure the sand box option is not enabled in the 3 server behaviors.
if you still get the same response, generate new api credentials.