Follow-up: I have an amazing friend who helped sort this out. Turns out there was a conflict between the FEC mod and the most recent security patch. The updateForm() function doesn't process properly with the new security in place. Our fix was to change the name of part of the function, and this has to be done in two FEC files.
includes/modules/pages/checkout/header_php.php:
Look for line 305:
HTML Code:
switch ($_GET['action']) {
case 'update':
$form_action_url = zen_href_link(FILENAME_CHECKOUT, '', 'SSL');
if (zen_not_null($_POST['comments'])) {
$_SESSION['comments'] = zen_db_prepare_input($_POST['comments']);
}
and change the name of the case 'update' to something else (something that makes sense, and doesn't conflict with anything else going on)
also change the updateForm function in includes/modules/pages/checkout/jscript_main.php:
HTML Code:
function updateForm() {
document.forms['checkout_payment'].action = "index.php?main_page=checkout&action=update";
document.forms['checkout_payment'].submit(); // Submit the page
}
Change the "index.php?main_page=checkout&action=update" - replacing the word 'update' to match the change you made in the first file. I changed them to 'upship' because it was shipping cost that I wanted to update on the page. I hope if anyone else stumbles into this issue this will help!