But I already registered? Why do I need to do it again?
Up to date, Freeview hasn't asked viewers to register or create an account to access any content. But if you streamed any TVNZ content through Freeview, you would have registered for a TVNZ account in order to watch TVNZ OnDemand.
This is because TVNZ OnDemand introduced registration a few years earlier, so you may think that you have a Freeview account already but in fact, you don't - what you have is a TVNZ account.
The Freeview registration is completely separate from the TVNZ registration - your TVNZ account isn't linked to Freeview since TVNZ currently do not have the authorisation to pass on your user information.