first step is to figure out why the shipping rate lookup is failing.
add this code to the failure page to see the full request and full response going to the shipping provider:
<?php
if(!session_id()) session_start();
echo "<p>UPS: <br />";
echo "Full Request: ".(isset($_SESSION["WA_Store_Cart_UPS_FullRequest"])?htmlentities($_SESSION["WA_Store_Cart_UPS_FullRequest"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["WA_Store_Cart_UPS_FullResponse"])?htmlentities($_SESSION["WA_Store_Cart_UPS_FullResponse"]):"n/a")."<br /></p>";
echo "<p>FedEX: <br />";
echo "Full Request: ".(isset($_SESSION["WA_Store_Cart_FedEx_FullRequest"])?htmlentities($_SESSION["WA_Store_Cart_FedEx_FullRequest"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["WA_Store_Cart_FedEx_FullResponse"])?htmlentities($_SESSION["WA_Store_Cart_FedEx_FullResponse"]):"n/a")."<br /></p>";
echo "<p>USPS: <br />";
echo "Full Request: ".(isset($_SESSION["WA_Store_Cart_USPS_FullRequest"])?htmlentities($_SESSION["WA_Store_Cart_USPS_FullRequest"]):"n/a")."<br />";
echo "Full Response: ".(isset($_SESSION["WA_Store_Cart_USPS_FullResponse"])?htmlentities($_SESSION["WA_Store_Cart_USPS_FullResponse"]):"n/a")."<br /></p>";
?>
NOTE:
the full request and full response will contain sensitive information that should be removed before posting here.