I have an “aeonSwitch” that is connected in line with a 3-way switch. I put it in a couple of years ago, and it works great. After switching to the new SmartThings app the device is not longer able to be toggled. It just shows the device, but that is all. No indication if it’s on or off, and no way to trigger it.
If it using a custom device handler, that could be why
Ah, it is. Do I have any recourse?
Try switching it to one of the default handlers. Z-zwave switch generic, zwave dimmer generic, etc.