Unreachable Status Reporting
As of this writing, it appears that a thermostat has a long delay (hours) before the Api reports that the thermostat is “Unreachable” or offline. The thermostat will report the last successful statuses and it will appear that the thermostat is normal. However, when you try to command the thermostat, it will fail with a connection timeout error.
Keep this in mind when troubleshooting failed commands. This can indicate an internet connection issue or a building wireless/device connection issue.