Add this PHP snippet in WPCode > + Add Snippet (Run Everywhere, PHP Snippet). This guarantees 100% automated delivery on every order:

add_action('woocommerce_order_status_processing', 'tg_send_order_whatsapp', 10, 1);
add_action('woocommerce_thankyou', 'tg_send_order_whatsapp', 10, 1);

function tg_send_order_whatsapp($order_id) {
    if (!$order_id) return;
    $order = wc_get_order($order_id);
    if (!$order || get_post_meta($order_id, '_tg_wa_sent', true)) return;

    $items = [];
    foreach ($order->get_items() as $item) {
        $items[] = ['name' => $item->get_name(), 'quantity' => $item->get_quantity(), 'total' => $item->get_total()];
    }

    $payload = [
        'id' => $order_id,
        'billing' => ['first_name' => $order->get_billing_first_name(), 'last_name' => $order->get_billing_last_name(), 'phone' => $order->get_billing_phone(), 'email' => $order->get_billing_email()],
        'total' => $order->get_total(),
        'payment_method_title' => $order->get_payment_method_title(),
        'store_name' => get_bloginfo('name'),
        'line_items' => $items,
        'apiKey' => 'tg_wa_sec_8780302089_techgigs'
    ];

    $response = wp_remote_post('https://whatsapp.techgigs.in/api/woocommerce?apiKey=tg_wa_sec_8780302089_techgigs', [
        'headers' => ['Content-Type' => 'application/json'],
        'body'    => json_encode($payload),
        'timeout' => 15,
    ]);

    if (!is_wp_error($response)) {
        update_post_meta($order_id, '_tg_wa_sent', 1);
    }
}

In WooCommerce > Settings > Advanced > Webhooks:

Name: WhatsApp Order Notification
Status: Active
Topic: Order created (or Order updated)
Delivery URL: https://whatsapp.techgigs.in/api/woocommerce?apiKey=tg_wa_sec_8780302089_techgigs
Secret: tg_wa_sec_8780302089_techgigs
API Version: WP REST API Integration v3