Duo Therm Penguin 15K heat pump

The check I suggested is to see if the compressor is being powered up but cannot start. Your system is what I'd call "complex" being Heat Pump and Wall Thermostat, but let's see what you find out.
It should have a Freeze Sensor which stops the Compressor if the Evaporator Coil ices up. I tinker with the simple systems, so I don't know what would happen if that Sensor fails or comes disconnected.
Do you have the Model Number for this Penguin? Maybe we can look up a wiring diagram.

The upper control board has a relay that supplies power to the Compressor. Then the Start Capacitor kicks in. I doubt your control board is the problem. Either the compressor is locked up or the Start Capacitor is bad. You do NOT have to purchase a NEW tstat if you buy a new Penguin. You just purchase a 12 button to 5 button change kit to install on the new Penguin to operate with your existing Tstat. This is best if you have 2 roof top units because you will have to replace the 2nd unit completely if you buy the new Penguin and the new 12 button tstat. 12 and 5 button control boards are not compatible. If you do NOT have 2 roof top units and just the One unit, then buy the new 12 button tstat as the change out kit and the new Tstat are about the same price. Doug

I,ll try this in the morning. Its a ducted unit with a 5 button thermostat.

Do you feel safe getting up on the roof to listen to it and do a few tests? If so, first thing I'd like you to try: With the system "cold", meaning you haven't been trying to operate it for half an hour or so... Have somebody turn the system to COOL while you listen carefully, right at the cover. What you're listening for is a CLICK. That would be the compressor trying to start, producing internal heat while trying, and a safety device popping open to prevent damage. You may not hear it over the fan noise.
This won't fix your problem but help isolate it. Compressor GETTING power but not starting is different from compressor NOT getting power.
This Penguin uses a Wall Thermostat, correct?
Ducted or not?
The easier troubleshooting is non-ducted units with no wall thermostat...

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