I recently purchased and installed a Leviton Decora Smart Dimmer 2nd Gen WiFi wall switch. I have had good luck with Leviton before. The switch works fine manually, with the Leviton app, with Amazon Alexa, and with Google Home. After some difficulty I can add it to my Smartthings home and assign it to a room, but it shows as offline even though everywhere else it is showing as online and works.
I wonder if the 2nd Gen Leviton devices are not yet in sync with Smartthings, or vice versa?