It's normal to install a new system and have your Zen Thermostat initially not work. Keep in mind your Zen was configured for your previous system. Please run through the Installation Page, and reconfigure the Zen for your system.
Note: If you have a home automation system you do NOT need to reconnect it to your system.
If you are still experiencing issues, please contact Zen support, and note the new system make/model if you have it - as well as any configuration details you can share.