I created a payment gateway as an addon. Everything seems to work except for the order completion page that we get redirected to after making payment from a third-party website.
The order completion page (fn_url("checkout.complete?order_id=$order_id", AREA, 'current')) is giving us a 403 error. Kindly advise what could be missing?
On post payment I have the following logic to finalize payment:
$order_id = isset($_REQUEST['order_id'])
Is this sufficient to ensure proper closing off of the order?