Checked thermostats upstairs. Switched 2 of them temporarily to test. After removing the ones that did not work for approximately a minute, they powered down and rebooted. The thermostats started working. Turned them on individually to check the damper operation. Did the same for the thermostat downstairs that did not work. Currently all 6 thermostats are operating properly. The zone system is a Trane Intergrated system which is older.