Group_concat on IF Select MYSQL

I have a query as below:

SELECT o.order_id,
       c.customer_name,
       Group_concat(p.product_name, ' x', p.product_quantity ORDER BY
       receipt_order ASC
       SEPARATOR
       '
') AS items,
       order_status,
       o.delivery_collection,
       o.order_total,
       o.payment_method,
       o.discount_value,
       o.order_time,
       o.order_note,
       IF(o.delivery_collection = 'delivery', (SELECT
       Group_concat(address_1, address_2, postcode SEPARATOR '
') AS delAdd
                                               FROM   address a
                                               WHERE
       c.customer_id = a.customer_id
       AND c.customer_type =
           a.customer_type), NULL)
FROM   orders o,
       order_products p,
       customer c
WHERE  c.customer_id = o.customer_id
       AND c.customer_type = o.customer_type
       AND o.order_id = p.order_id
       AND order_time > Now() - INTERVAL 72 hour
GROUP  BY p.order_id
ORDER  BY order_status DESC,
          o.order_id DESC

The problem I have is that the Group_Concat() inside the IF concatenates but it doesn't include the separator and is not called delAdd. I have also tried CONCAT_WS and CONCAT but all are giving the same results. I am using MySQL 5.6.43 on 10.3.18-MariaDB server.