It would be easier to troubleshoot why the shipping and checkout in power store are not working than to recreate it using eCart.
to troubleshoot the problem add the following to the checkout_failure.php page in the body:
php:
<?php
if(!session_id()) session_start();
echo("Paypal Full Response :<br />");
echo("<code>".isset($_SESSION["PP_DirectPayment"])?$_SESSION["PP_DirectPayment"]:""."</code><br /><br />");
echo("USPS Full Response :<br />");
echo("<code>".isset($_SESSION["WA_Store_Cart_USPS_FullResponse"])?$_SESSION["WA_Store_Cart_USPS_FullResponse"]:""."</code><br /><br />");
?>
This will return the response from the USPS and PayPal server on failure, with this information, we will be in a better situation to understand why they are failing.
