breakers are worth checking, as well as resetting the EMS.
But I blow AC breakers all the time trying to run AC in my driveway on 30 amps, when it happens, the thermostat indications are still normal, both sones selectable, whichever I set indicates cool. Units themselves won't run without ac power, but the thermostat always indicates right.
And then when I reread the OP's post, he does say the thermostat is lit up and he can select and control both zone.
(Where did all this about dead thermostats and or bad comm cables come from?)
The EMS in my unit will cut loads based on input power, and it knows when I plug into 30 amps. The first thing it sheds is the rear AC, and the lights on the EMS panel show what is currently being powered.
In my driveway, I have a 20 amp circuit. It can deliver maybe 24 amps, but the voltage drops to around 105, and the breakers for the A/C's (whichever one I'm Trying to use) will blow.
The magnum inverter trying to charge the batteries can suck 9 amps or more, really gumming up the works.
Check your breakers in the rear closet. Flip and reset the ones for both A/C's.
You can reset the EMS by flipping the main breaker off then back on, You'll hear the relays click as the loads power on, and at this point all the green LEDs on the EMS panel should be lit.
Then try your air conditioning again.