Similar situation here. I was told I would get the chance to choose a seat when check-in opens. We used AA miles to book DEN > LAX > NAN > AKL for a trip next month. The ticket was booked last year. The Fiji website is close to useless. It won't save flyer info and has a confusing seat selection process.

We were initially assigned seats when the award ticket was booked on AA.com. A couple of months ago, I went to Fiji's site to check our information is correct in their system. Then, simply by trying to see what we'd been assigned, I accidentally gave up our free seats. I tried emailing and calling Fiji's CS to get the free seats reassigned. They would not budge and gave me the run around. A rep told me they used to give seat assignments with award ticket but started charging in 2023. When I brought up my ticket was issued last year, I thought I had finally gotten them to reassign, but then never got the call back I was promised.

I didn't want to risk being separated or a less than ideal seat on the long LAX > NAN leg. I decided not to waste any more of my time on it and just pay the $33 pp to try and block out an economy row. Was tempted to pay $120 pp for one of their "Bula" seats but by the time I was done going back and forth with CS all the Bula rows we wanted were taken. I researched their plane config a bunch online and the Fiji economy seat seems quite narrow. Bula seats basically just gets you a couple inches more legroom so I'm not sure it's worth the additional upcharge unless you're long legged.