Why can't I update my GS4 I9500 beyond 4.2.2?

[AC Question]

Why cant I update my GS4 I9500 beyond 4.2.2?

I have tried in phone setting, and in Kies over and over again. I have downloaded root checker to see if this phone is rooted but it says its not (I've read that blocks updates). It was factory reset when I purchased it and working fine, just confuses me as to why I can't update.

I have tried to find the necessary New Zealand update to do it manually via odin but I can't find them anywhere.

Thanks for any help!!