If your Lennox thermostat is unable to communicate with the smart hub, troubleshoot by ensuring both devices are properly connected to the same Wi-Fi network. Check for any obstructions or interference that may hinder signal transmission. Restart both the thermostat and the smart hub to refresh their connection. Ensure that the thermostat firmware is up to date and compatible with the smart hub. If the issue persists, consult the user manual for specific troubleshooting steps or contact Lennox customer support for further assistance in resolving the communication problem.