Central locking button

[Signal green]

I picked up my 1998 993 4S today, on driving it back home I pressed the central locking button on the centre consul and the light illuminated on it, when I got back too my garage I got out of the car too unlock the garage, I left the car running and shut the door, when I came back too open the door they wouldn’t open and the central locking button was still on, should the central locking button disarm once you open the doors or do you have to disarm it by pressing the button
Thanks