hatchy

Hey all, I am a total Newbie to GR2. Just hired it from the video store but can't get the action button to work. I was doing the training session and it got to the part where I take control of an enemy machine gun but it won't let me grab it. A symbol appears top centre of screen and I hit the "O" button on the controller but nothing happens. Can anyone help. Would be much appreciated. Thanks Dave p.s. I am using PS2 console