it works by itself, try NOT using simhub first. Then, if you figure it out, try adding simhub back in.
Start the lights program before launching rf2. Then, to make it easier to see if the lights are flashing, set the practice start time to something after 10pm. I've noticed at a few tracks, in daytime, the lights don't illuminate brightly enough to easily see from the cockpit.
You can also verify by using the page down key for the exterior view and then either the numberpad 4 or numberpad 6 to rotate around to the front.
Finally, if you have your message center enabled, where it tells you in text that you pit crew is ready, or you have a penalty, in that box, you should see it toggling between "headlights on" then "headlights off," over and over til you exit the pit lane.