Thermostat not adding in like others

I installed a thermostat on the first floor but was not able to get it to communicate with the panel? Any ideas why not?

If you are having trouble adding a Zwave device to your network, always try to remove the device. Press the remve the device button, then perform the pairing procedure on the device. (I would suggest just doing this as your first step regardless.) Zwave devices can only be attached to one network at a time. See the instructional page found here.