Hello, do your taillamps work for each rear set as well as the tail side marker? They are on the same circuit as the Right and Left License plate lamps, so you should check for power at each License plate bulb location first, if there is power there (12v) it might be a bad Ground for the License plate lamps, they both Ground on the Left rear Frame Rail. I'll post a diagram for you. The ground looks to be a white wire with a black stripe.
Here are the aftermarket and Toyota OEM diagrams for the Tail/License plate lamps:
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.