Important to note: what kind of card do you have?
while most of the current UA cards allow premier access (and thus BG2 and full size carry on in BE), not all do. Specifically, thinking of the TravelBank card currently out there, as well as legacy cards which don’t offer it (for example, I have the Select, which isn’t available anymore, but doesn’t include priority boarding). If it’s the Explorer, it works. So just make sure your card is eligible.