The version you have doesn't contain one of the possible causes, but the other possible cause is still likely.
Try removing the valve socket board (it pulls straight up after the valve is removed) and reinstall. It's possible that one of the carrier contacts is not fully seated. Also, be sure there is no stress on the valve, the retainer should just touch the valve and not push it to the left.
Also, make sure that all screws are snug on the bottom of the chassis.