The lights work off a switched ground. Your lights are all working properly other than the switch setting, so either you have bad switches or there is a missing ground bus on the light that feeds the switch. Ground is supplied by 2 of the 4 screws that fix the housing to the roof. If you remove the light it should be obvious if checked with a meter.
You, sir, are a gentleman AND a scholar. Thank you, that was spot on - works now.