Sorry to hear you haven't received your order.
When an order is out for delivery our delivery partners will attempt to deliver it 3 times. If they can't deliver it, the order is returned back to us for a refund.
Sometimes there might be problems finding or accessing the delivery address, and if the attempts are unsuccessful, the order will be returned.
Occasionally, an order gets damaged in transit and can't be delivered.
You should be able to check the reason why it's been returned by using the tracking link you got in the dispatch email.