I have a very similar to this machine with the cam door.
Rotating the large knob to the right of the door clockwise dis engages the door latch.
I’d suggest rotating that knob slightly left to see if it trips the latch.
Otherwise, remove the top cover and look to see if the springs and latches are all connected.
https://www.youtube.com/watch?v=2MTzrVmG-n8