I am trying to install a Kasa HS210 smart switch in my basement/garage. 5 light fixtures are installed in the ceiling with led lights attached. There are 3 switched controlling these lights, a three way switch at one each end and a 4 way in the middle. When the smart switch is activated, the lights flash off and on. I then have to switch both of the other switches to get them to turn back off.
I ordered an additional switch to make sure it wasn’t a bad switch and got the same results.
The first three way switch has white connected to the black screw and red and black travelers. There are no commons in this box. There is an additional switch going to an outside light.
The second switch is a four way with the red and black travelers. There is another three way switch on a different circuit going to a stairway.
The smart switch is in the third location. There is another switch in this box going to an outside light. These are on the same circuit.