Uh-oh! I'm sorry to hear that you can't add your thermostat to the app. The TD023 code means that your thermostat may be out of range or not powered on. Did you try using the Help Center or troubleshooter before contacting support? If so, which steps have you tried already? If not, you may need to do an account connection reset on the thermostat because it doesn't show as an available Bluetooth device if it's on an account, or follow these steps:
Quit and restart the Nest or Google Home app.
Make sure Bluetooth is on. Turn Bluetooth off, then back on to refresh the connection.
Disconnect any Bluetooth devices that are connected to the phone to rule out any interference.
Put the mobile device on airplane mode, then turn on Bluetooth and Wi-Fi.
Restart the phone or tablet.
Restart the joining and assisting devices.
Move the joining device closer to the router, or the router closer to the assisting device.
Try a different mobile device.
Create a hotspot and try to pair again. Make sure that the device connects to the hotspot this time and not the home Wi-Fi.
Create another structure in the Nest or Google Home app and try to add the device to the newly created structure.
