There should be a switch between the two map lights on the ceiling light that you can switch to the left for off, to the middle for auto on when the doors are open, and to the right for on all the time.
Set that switch to the middle and you should be fine. If it doesn't go on, then you have another issue going on.
There should only be 3 switches total. One switch for each map light, turned to off when not in use unless you want to drain your battery. The center switch should be in the middle position, and will come on when the doors are open.