If your visa application declined then, you probably did not meet the requirement of being a bona fide applicant. Bona fide means genuine. It means the intention of every applicant for a temporary visa application must be real.
Bona fide means:
You genuinely intend to stay in NZ for a short period.
You will remain in NZ legally which means you will not demonstrate any risk to overstay.
You will not break any law or rule while you are in NZ.
You will not break conditions in your visa.
If you are not from visa waiver country, sometimes it is tricky to prove you are a bona fide visitor. If your temporary visa (visitor, student, etc.) application was declined and you were given an explanation by Immigration Officer that he or she didn't believe you are a bona fide visitor, then please consult your case with Immigration Trust.
Your immigration officer must give you written reasons for his or her decision to decline your application based on immigration instructions. If there are other reasons for Immigration Officer to decline your application. In this case, you could apply for a reconsideration of your declined visa application.