I am trying to complete Task Logic tutorial 4.3 but I can't seem to get the elevator to behave the way it is supposed to in Step 6. After the first AGV takes the elevator up, the elevator stays at the top and does not return to the first floor to transport further AGVs. I must be doing something wrong, but can't figure out what it is. I have checked and rechecked my work. I have even recreated the model again but can't get it to work. Please help!