Currently line 358 is:
<?php if ((isset($_POST["CheckoutWizard_submit"]) || isset($_POST["CheckoutWizard_submit_x"])) && $_SESSION['WAVT_confirmcart_Errors']=="" && !isset($_POST["forShipping"])) { ?>
You could add another check to that like:
<?php
if ((isset($_POST["CheckoutWizard_submit"]) || isset($_POST["CheckoutWizard_submit_x"])) && $_SESSION['WAVT_confirmcart_Errors']=="" && !isset($_POST["forShipping"])) {
if (!$_SESSION["eCart1_UPS_Quote"]) {
?>
<strong>Unable to find that shipping address. Please make sure the entered address and zip code are correct.</strong>
<?php
} else {
?>
Then you would have to add another close bracket to the php code above the fins </div> (there is already one there you would need two, so update:
<?php } ?>
to:
<?php } } ?>