Unfortunately we are unable to follow up any further as the parcel has been marked as delivered by Australia Post, as Australia Post has terms and conditions that don't allow us to track past delivery for security and privacy reasons (to protect the recipient).
We would suggest that you speak with the staff at the post office just in case it has been taken there for collection and you can also call Australia Post customer service Helpline 137678 or log a tracking enquiry via their website or your tracking link.
Please feel free to get in touch with us if you need further assistance.