to troubleshoot the paypal express checkout issues, add the following code to the failure page:
<?php
if(!session_id()) session_start();
echo "<p>Express Authorize: <br />";
echo "Full Request: ".(isset($_SESSION["ECO_Auth_Request"])?htmlentities($_SESSION["ECO_Auth_Request"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["ECO_Auth_Result"])?htmlentities($_SESSION["ECO_Auth_Result"]):"n/a")."<br /></p>";
echo "<p>Express Process: <br />";
echo "Full Request: ".(isset($_SESSION["ECO_Process_Request"])?htmlentities($_SESSION["ECO_Process_Request"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["ECO_Process_Result"])?htmlentities($_SESSION["ECO_Process_Result"]):"n/a")."<br /></p>";
?>
this will write the full request and full response from paypal to help determine what is wrong
NOTE: The full request and response will contain sensitive information that should be removed before posting here.