This may be because there are so many different reasons that an owner finds their phone Prenormal, but they don’t know why!
In this post are many causes KG or RMM State Prenormal.
My guess is that this is the reason. One cause of Prenormal is that the phone is new (usually) and the phone has not proved to Samsung RMM that it is in normal use.
Samsung’s “rules” can be different, but in Europe we have seen (at some time) that Samsung expects a user to make 5 minutes of calls in the region where the phone was intended for sale.
Other times the 5 minutes calls are not “a rule” but the phone must be shown to be in normal use for 14 days. Sometimes a user finds with a SIM installed and WI-Fi connected simply checking for updates lifts Prenormal to “Checking” and this is enough to allow “non Samsung binaries” to be flashed, that is a Custom ROM or TWRP.
You might check with a local Samsung community support group on their knowledge of local rules https://r1.community.samsung.com/t5/new-zealand/ct-p/nz?page=1&tab=recent_topics but I would say that you should just get a SIM in it and commence using it “normally” soonest.
Should you have bought the phone recently, new or refurbished, I guess you should also try to establish that the phone was being sold in its “intended market”, that is that it is not a “grey import” from say, perhaps, an Asian country to NZ.