Postie refused to deliver and I will lose money as a result

I ordered an item for a business dinner (tomorrow night) weeks ago. First the item was broken at the sorting centre. It was redelivered and due to arrive today. No signature necessary, delivered to a back unit, safe area, no issues. Next thing I know I get a notification saying item could not be delivered due to locked gate. I DO NOT HAVE A GATE. I have sent complaint to the official complaint centre and they are brushing me off. This is actually going to cost me money if I don’t have it for tomorrow night - how much can I escalate this? And why the hell can the postie refuse to leave a package that is clearly labelled as such?