cubase and reason...... simple question?

How do I set up Cubase so that when I hit record (in cubase) play and record begin at the same time along with the mpc. I had it working perfectly before but now it wont work....when i hit record, the red button "lights up" but the track doesnt begin/.......when i hit play, the green button lights up, the mpc and cubase start but the red record light goes out (in cubase).....I know there is something simple i need to adjust but I read the cubase manual and am getting nowhere.
Peace
O