Switch was replaced and works, so chalk it up to being one of the ~10% GE failure rate.
Pairing the GE switches is always such a pain. Every. Single. Time (using the St phone app).
I’ve been able to pair the GE in-wall toggle switch using both the "GE On/Off Paddle Switch (z-wave), and the “GE 3-way, in-wall on/Off Switch Kit”.
The latter is misleading in that there is a note at the bottom of the “Connect Now” page stating “Automatically turn a light on or off from two locations in your house - such as at the top and bottom of a staircase-or anywhere with your smartphone”.
This led me to believe that this is exclusively for a 3-way switch, when in fact it can be used for a single switch.
When you tap “Connect Now”, the switch is rarely found straight away. As mentioned by others, you turn on the switch for 5 seconds, and then off for 5 seconds. Wash, rinse, repeat. Wash rinse repeat…On occasion this works.
Sometimes it will find the switch, but you don’t know it until you completely back out of the “Connect Now” page to the “Marketplace”, where hopefully you’ll see “Device waiting for configuration”.
Other times I’ve completely closed the ST app and restarted it. Only then am I able to pair the switch.
For something that is on the ST approved list, it sure is a PITA to pair. It takes me less time to figure out the line/load/neutral/ground wires, throw the breaker after figuring out which one it actually is, remove the dumb switch, install the GE switch, and turn on the mains power than it does to pair the switch.