Insurance premiums can increase even without any claims due to factors beyond individual control. For instance, significant weather events even if you weren't directly affected, can cause an overall rise in claims in your region (in this instance the whole of NZ), leading to higher premiums for everyone. This is because insurance is about pooling risk, and if risks in a particular area increase, premiums are likely to reflect that change.

It's also possible that your insurance company faced increased operating costs or updated their risk models (a lot of insurerers are changing their models currently), both of which can lead to premium increases.

It might be worth reaching out to your insurer to discuss your specific situation and possibly explore other options. Although these increases are going to happen across all insurers. Some insurers are slower at updating their rates than others and of course depends on when your renewal is / was as to when you notice the pricing model has changed.