I have a DewStop FS-300-W1 humidity sensor that replaces a light switch that has a red, black, white and green wires. I want to replace the left most switch (that currently controls the fan) with the humidity sensor, in the 3-gang box in the photos. The fan it above the shower a few feet away, and the 3 gang box is on the wall near the door entrance.
In the photos, the switch on the left currently controls our fan. Its connected by two black wires as shown. Any ideas on if I can wire this properly? I tried a few combinations but couldn't get it to work. There is a series white wires tucked away in the back that I did not test.