Exploring time travel reveals that backward travel to any point before a machine is constructed is theoretically prohibited, whether framed by the universe’s need to avoid paradoxes (such as Stephen Hawking’s Chronology Protection Conjecture) or by simple physical geometry (like the Earth’s movement through the galaxy)
It was powered at the source time, but since the building the machine was in didn’t exist in the destination time the plug simply fell to the ground.
ETA: The door has a handle, so it’s obviously not automatic like some Star Trek door.
Exploring time travel reveals that backward travel to any point before a machine is constructed is theoretically prohibited, whether framed by the universe’s need to avoid paradoxes (such as Stephen Hawking’s Chronology Protection Conjecture) or by simple physical geometry (like the Earth’s movement through the galaxy)