Night time running lights not working

Which lights are on during the day? If you turn the light switch to on at night the lights still stay off? That car should have a switch that has off, on and auto. With the switch in the off position the daytime running lamps and dash will work, but no other lights other than brake lights. In the on position all the lights will come on and you have high and low beams. In the auto position the daytime running lights work but once it gets dark the system will switch over and turn on the lights like you turned the switch to the on position.
What spot is the switch in? Next if you turn the switch to on do all of the lights work?
Trying to narrow down where the issue could be.

To me it sounds like the BCM is going out. To be sure here is a video that shows how to run the codes (CAN scan) and the DRL wiring diagrams so you can see how the system works with the BCM replacement instructions as well:

https://youtu.be/InIlnsjOVFA

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Okay, if using the main switch also does nothing to turn on the lights it could be either the body control module or the park lamp relay in the junction box. However, as you say they do work but then stop working once it gets dark I would start with a dealer level scan tool that can control those lights and use it to test the relay and to watch what the ambient light sensor on the dash does as it sounds like that is part of the problem. Here is a quick test. The sensor is the small dark dome in the middle of the defroster grid up by the glass. It tells the BCM if it is light or dark and to turn the lights on and the DRLs off when it gets dark. If you turn the switch to auto when it is light out and you see the lights work, take a piece of cardboard or other item that light will not pass through and set it over the sensor to make it think it is now dark out, what do the lights do now? If they go off then using the scan tool will be the best way to determine if the system is turning the relay on and switching over. Unfortunately the BCM could still be the issue. That should show up in the testing.