You may be on an aircraft with the Polaris cabin (hard product) but you are flying on a flight that offers domestic first class service (if you look at your reservation it will say something like "United First (P)" or "United First (J)") -- access to the Polaris lounge is offered only to those on long-haul international flights where the cabin is marketed as United Polaris Business (the reservation would show this as the cabin/fare class), generally Europe, Asia, and parts of South America (the Caribbean, Mexico, Canada and Hawaii do not count).

Similarly you would not have access to a United Club location absent either *G status or a UC membership. On short-haul international flights (like the regions I just mentioned) where the front cabin is marketed as United Business [note no "Polaris"] you would have regular club access -- but again Hawaii doesn't meet this requirement as far as United is concerned.

Since it can be confusing and perhaps to help with where to look, here's a random ORD-HNL (United First) flight compared to a random ORD-FRA (United Polaris Business) flight on the same day