this problem may be due to a php bug where session information that is s=created before using the header function to redirect to another page is not saved.
on the Products_Detail.php page. locate the following code:
<?php
// WA eCart Redirect
if ($WA_Store_Cart->redirStr != "") {
header("Location: ".$WA_Store_Cart->redirStr);
}
?>
and change it to:
<?php
// WA eCart Redirect
if ($WA_Store_Cart->redirStr != "") {
session_commit();
header("Location: ".$WA_Store_Cart->redirStr);
}
?>