I have a very puzzling problem with an Add-On switch installation. For starters, I am not sure which is the main switch and which is the secondary. However, when looking at the switch that is upstairs, closest to the light, I see 1 black (line) 1 dark gray (load) 1 red (traveler) 1 white (neutral) 1 ground.
When looking at the switch down the stairs, I see 1 dark gray, red, white and ground.
After I plugged all the wires into the new in wall switch upstairs, and into the add on switch downstairs, I was only able to turn the light on, and no matter what, cannot turn it off.
The thing that puzzles me the most is that in all youtube videos I see in the add on switch box, there are 2 blacks, just like the main switch box, and these 2 get piggy tailed together. I only have 1 black in my add on switch box.