Hello, there is no field NOTE in table ORDERS in early prestashop 1.7 versions. The NOTE field have appeared in later prestashop 1.7 versions. Then, you can try this code:
 
if (!empty($message) && Validate::isCleanHtml($message)) {
            // Retrieve the last created order for the current cart
            $order = Order::getByCartId((int)$id_cart);
            if ($order) {
                // Sanitize the message
                $cleanMessage = strip_tags($message, '<br>');
                // Update the note field in the orders table
                Db::getInstance()->update(
                    'orders',
                    ['note' => pSQL($cleanMessage)],
                    'id_order = ' . (int)$order->id
                );
            }
        }