Hi Andrew
I had exactly this problem once with a WNW package and after I emailed them, Dave Johnson had it sorted out very quickly. Not sure what the reason was but the package would not scan at NZ Post so it went nowhere. All fixed quickly.
Even allowing for extra pressure on them over Christmas releases a kit ordered on 24 November should have been delivered by now.
The good news is Wingnuts are absolutely reliable to deal with and any issues with your order will be made good by them.
Email a copy of your shipping notice to Wingnuts which will give them the order reference and tracking number. If you did not receive a shipping notice then the problem is in the Wingnuts system, not NZ Post.
Dave Wilson
Gold Coast
Australia