No sound output from my overdrive channel on my amp?

i have a crate fxt120 amp with a 3 button foot switch and im getting no sound whatsoever out of my overdrive channel. can someone tell me what might be the problem? and also where do i plug the two cables that go into the footswitch after i plug them into the back of the amp? there are two holes but i am not sure which cable goes into which. or does it matter?