Vanished postal item

A postal item departed from New York at 11 pm on 27 October 2017 departed 11.20 from Dubai on the 29th. It departed from Johannesburg INTL at 25 pm on the 30th for its destination in Cape Town. I have been to the Post Office twice with the USPS tracking number, but received the reply "No information." I also sent an email to ********** on 21 November 2017 but didn't even receive an acknowledgement, never mind a reply. So, what to do?