[2022] new york not available to my hard core character

I have 4 full blown normal characters under my main login on my xbox. I didn't want to delete any of them, so I started a hard core character under my son's xbox account (on the same xbox that the game & expansions are installed). But when I finish tidal basin, it acts like I need to purchase the expansion? Shouldn't it already be available of it's installed on this xbox?