Maybe check if the overlap event occurs at all with a print string message. You can also put another one into the cast failed pin. Try to narrow down the problem.
Sometimes little things can break blueprints. Maybe begin overlap never happens because they are already overlapping when the rooms are constructed. Weird things like that.
Then if the overlap event happens check what is overlapping with print string of its name.
That ‘is overlapping actor’ node might be double checking. You’re box causes the overlap event so you don’t need to check again if it was overlapping?