I have a penguin rooftop ducted system with analog

If you have no leds, then you have a power supply problem. I am assuming that you have the Dometic Electronic Control Thermostat with the ribbon cable connection. Check for 12V power at the control board in the air conditioner, Red 12V+ and Black 12V-. Make sure polarity is correct. If you have power there then check the number 1 and number 10 pins on the ribbon. The voltage should be the same. If they are not, then you have a bad control board, not thermostat.

Hope this helps,

Jeff