Cant Add Honeywell to SmartThing Hub

Hi all, hoping you can help.

I have a smartthings hub that has been working for a while. However, when I try to add a new honeywell z-wave thermostat, it tells me it cannot add it.

All my existing thermostats are reading and the hub displays as connected.

Stranger than this, I reset an existing thermostat so I can troubleshoot. I then tried to add it back to the hub, but got the same error.

What could be the cause?


If you are using any custom device handlers for them, then login to IDE, open the device handlers and Publish for Me again. Then exclude and try to pair the devices. There is a known issue where device handlers can become stale and preventing new devices from pairing.

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Sorry, I’m not too familiar… what would a custom device handler be?

iDE is but doesn’t sound like you used custom code. You may want to contact ST support directly at

When I had this problem, I had to go to my HWell account and remove the ST assignment. Then, when I reconnected it worked. However, it took about an hour before that connection happened. It has worked well ever since. I also noticed that to have it, the thermostat, show in the Google Asst., I had to refrain from directly connecting to the GA and, instead, connect it through ST. That was my experience.

Dan, how does this work?
These are z-wave thermostats. I am not using the honeywell app to read them; only smart things.

I installed mine (RTH6500 WiFi Series) using the TCC app which required also using the computer. Once that was proven usable I used the ST New App to add the Honeywell device. For some reason that took a couple hours to show up in the ST app. Once it did, it became visible to GAsst. I found any other sequence of events or trying to connect the thermostat only to GAsst did not work. The voice and app control of the device has been working without error since, about 1 year. Let me know if that helps.

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