You need to go to the left side of the castle in the construction room to open the menu and repair the reception room.
After talking to Kostyx about his recommended student/pupil, the progression to build the reception ends there. The interaction marker doesn't pop up. I'm assuming the table in the corner of the mission room is meant to be the construction table? That isn't highlighting.
I have reloaded from the autosave, and still nothing. I am on the public demo version, not the paid/subscribed version.