As far as I remember you need to start Tracer's route to get into girl's dorm and that's where your cooperation with Sombra begins. After that, just do her quests until you get to the route.
thank you and i just wanted to report a possible bug , i finished most routes and was on the hana route and now all my save data is gone idk why but i know i saved before exiting and now its all gone so im not sure if its a bug or something else
edit: it just now popped back with my saves so idk
