Hi Tom,
You need to open up your synth and check that CN3 and CN5 are plugged in correctly.
I would say that either they are plugged in swapped over or one or both of the connectors are plugged in with the pins offset (difficult to do but not impossible). Check that CN3 is plugged into the CN3 row of pins (the cables are marked with "CN3" or "CN5" on the white connector plug) and that CN5 is plugged into the CN5 row of pins.
Mike.