You are right, it was because I didn't talk to Hermione in one location, it was resolved very simply. As for demolishing the Hangout Room, I did it a few times before I figured out the problem, it doesn't seem to have affected the stability of the game so far. The most important thing is that its construction after demolition does not require money - 0$
But this case convinced me that it's becoming badly needed (though not in the next update, but in 3-4 updates) a hint system or quest system as it is in games like High School Days, Summertime Saga or Amnesia.