With ignition on, and everything still connected, check the voltages on the interface unit:
pin 11 (clutch) should be 12v going down to 0v when you press the clutch.
pin 4 (brakes) should be 12v going to 0v when you press the brakes.
pin 6 (brake check) should be 0v going to 12v when you press the switch.
I think I have these the right way round, but the most important thing is do they change when you press the pedals? If not your adjustment isn't right, the switches are faulty, or the power feed to the switches may be missing.