When I open the tailgate of my 2014 Sienna Limited, all the interior lights come on including the one on the right side of the luggage area. There is an external light switch for each of the side door but the light switch for the hatch door is apparently in the latch.
Do all the other interior lights come on when you open the side and hatch doors? If not, check to see if the master interior light button in the overhead console is in Off position.