The new taillights have an internal harness for the LEDs which are simply connected to the OE harness. Remember that a diode is a one-way electrical path and if the polarity is not correct they will not light up. Since the plugs can be connected either way it's easy get the polarity reversed. Reverse the plug on any LED section that doesn't light up by testing their operation now, before bolting everything back together. Even though Mr. Bodykit included a flyer with a notice to this effect we got a couple of them backwards anyway.