You need to activate triggers. To get to the second floor, the scheme is approximately the following. Be sure to finish the first scene in the pantry with the girl with the glasses. After that, you need to meet with a pink-haired girl in a bar (whether you win or lose to her is not important). After that, you need to talk to a man in a hoodie in the toilet, he will say that in order to get to the second floor, you need to have sex with three girls. After doing this, you need to talk to the guards on the second floor (they are standing to the right of the stage), they will ask for a pass. Again, talk to the man in the toilet, he will issue a task for a pass. After completing the task, you will need to go to the rightmost toilet cubicle, open the dialog box and press the "knock" button three times and then "speak".
Like that. Where did you end up in this chain?