I dial 640 and still nothing
640 is a call forward code. You would dial 631 from the attendant phone except you say you have the button that cycles through the modes. I would confirm the button is programmed correctly though. You can do this by taking the station off hook and dialing [speed] + 7 + # and select 2 for keyset buttons.

You could also check to see if another station is allowed to place the system into night mode with a button programmed with feature code 604.

- Dave S. -

You can never appease your ideologue opponents.