machine tending door open/close automatically

(1) A Process Machine - ProMill is used in the layout. A arcMate_120iC10L is used to load/unload parts for the machine without Robot Manager V4. Once the robot put the part in the ProMill, the ProMill automatically close its door and start to execute. When its oparation finished, the door open automatically again. Why the ProMill can operat automatically without any signal? It’s not even connected to the robot.

(2) Robot unstacks materials and loads them one by one to the ProMill. When the first material is sent to the ProMill, the ProMill will automatically open and close. But in the second loop, the machine will not automatically close the door and execute. Why?

My software is version 4.0. Can someone help me? Thanks.