I've installed an HS210 three-way kit to control some hallway lights. I've done the wiring perfectly and the setup went without a hitch. However, there's a problem now.

The first switch turns the lights on and off just fine. So does the app. However, the second switch that I installed (the one you set up second) will not turn the light on if the first switch is set to off and vice versa.

Basically, it's like the second switch will not sync up with the first one.

I have another HS210 kit installed *in the same hallway* and they both sync up their statuses and control their lights just fine.

What. Is. Happening?