I have purchased Xanathars guide to everything, and it says that the content is unlocked, however when iam choosing a subclass for one of my characters, namely gloomstalker, it only has the basic choice and playtest available, how do i fix this and use the xanathars subclass?

It might be a caching issue with the browser not pulling the updated info. Maybe try logging out and back in and see if it pulls the updated info. It seems to have worked for some users, and there’s no way it can hurt anything.