By the way, I had another flight recently, HND to FRA, this time a paid PremiumEconomy in an upgradeable booking class. I requested the upgrade to business class but was not cleared. The person sitting next to me on the plane also complained that he did not get upgraded, lol.

I think getting upgrades to business class is extremely difficult at the moment, I assume everyone is sitting on a lot of miles/upgrade points. Unless you are diamond, I guess you should not get your hopes up. I am platinum at the moment, it didn't help for the waitlist priority… :/

I would say upgrades from Economy to Premium Economy seem to be much easier. Requested one recently and was cleared a day in advance.