There are several items you can check. First check that the thermostat is set to the Cool position. Make sure the temperature is set lower than the Inside temperature reading. Also check the circuit breaker and reset if necessary. Make sure that the furnace door is closed securely. If “wait” is in the screen or “cool on” is flashing – wait 5 minutes for the system to safely respond. The thermostat will indicate it is asking for the cooling to turn on when "cool on" or a "snowflake" in the display. If this message is in the display, the thermostat is asking for the heat to be on and there is a likely a problem outside of the thermostat preventing the cooling from running.