ST Not Updating Honeywell YTH8320ZW1007/U Thermostat

I’ve had this thermostat for three years now with no problem, but in the past week, the ST app and Alexa have stopped being able to control it. The thermostat still reports to ST, so if you check the “Recent” tab it is accurate on when the A/C runs or what the temp was set to.

If you adjust the temp on the app, the app says the temp has been changed, but it hasn’t if you check the thermostat. Any ideas on how to even start troubleshooting this?

Thank you for your help.

I’m seeing similar issues, where the thermostat is actually reporting active state correctly to SmartThings, but I can’t change the temperatures from it. The Honeywell app works fine as does Alexa (using the native Honeywell integration, not via SmartThings) - but ST simply can’t change the temperatures.

If I click the ‘mode’ or ‘fan’ buttons it does cycle those properly, and the ‘recently’ tab seems correct as does the current state. But the Heat/Cool buttons don’t do anything.

I’ve monitored the logs while making temp change requests from the ST app and I do see update requests to the thermostat - but when monitoring the thermostat itself I don’t see those changes being reflected.

I got mine working again by excluding it from ST and then re-including it.

How did you do that, by just deleting the SmartApp/Device and re-adding?

From the thermostat, you select the option to put it in exclusion mode (I had to get the manual to see how to do it), then in the ST app, I told it to exclude the device. Then I changed the thermostat to inclusion mode just like I did when I first configured it.