Yes this has been an ongoing issue with Airnz on the long hauls - the cabin crew tend to be very conservative about when windows are undimmed, often waiting until the approach. I understand it's to do with allowing any remaining BP sleepers who have elected the "sleep-in breakfast" option to continue to rest, which doesn't help Y or PE pax who have been up for hours by this point. Like others have mentioned, ask the most senior FA in your cabin class nicely if they can individually unlock your window. Tell them you are feeling quite motion sick and being able to see the horizon would alleviate this and hopefully mean that you aren't calling them over to your seat to hand them a filled brown paper bag. I'd also make sure to provide feedback on the passenger survey.

American Airlines discontinued the practice a couple of years back

https://simpleflying.com/american-dreamliner-windows/