It depends. Some companies will ditch the parcel and run, which forces NZ Post to take it, which is a bit of an asshole move. Others will attempt to deliver, obviously find that they cannot, and then wait for you to contact them so it can be delivered to a different address / picked up from a depot. Sometimes a company will just redirect the parcel through NZPost so it can be recieved.

So many sellers fail to be transparent about which company they use and the way parcel collect is set up is absolute nightmare for everyone involved. Best you can do is contact the courier and get it redirected to another address / organise to pick it up from depot.