No tail lights

It is nice to have a test light for checking something like this, to see where the power ends. A lot of time it is at the plugins in the wiring for the tail lights, brake lights and such, just a matter of unplugging them and plugging them back together. With a test light you could see if there is power to that point to know if you need to look back further into the system. Also try moving the bulbs around in the sockets with the tail lights on to try and make contact.