I chatted with a manager this afternoon (EST) about this issue. NH159/160 is not showing up in their system. They are well aware of it at this point. He insisted that they have no way to request a seat from NH for a flight that is not showing up in their system (even if the flight and seat are showing as available with other partners).

It may be that someone broke protocol for tdot_guy and pulled some strings. I remember previously reading of at least one case of this happening during COVID when some routes simply disappeared. Not cancelled, just removed entirely from the system. Regardless, at this point one isn't going to be able to get VS to book this flight pair until it's in their system, which is too bad because after 24 hours of repeated calls and gambling that they'd get their act together, the seat I wanted to book is now gone.

Regarding government approval, while nothing is certain in life, this isn't something I would worry about. Whether it's the official reason VS can't book I cannot say. It's a bit fishy considering the other partners can book. Still, it is true that NH does not yet have full approval. If you look up the flight from ANA it notes that the flight is pending regulatory approval. I remember seeing flights initially listed in this manner when they changed a bunch of routes from NRT to HND for the olympics.