First thing I would do is check for power at the A/C. Sounds like it's not there.
Next I might think of taking power to the A/C with a heavy duty extension cord just to see if it runs period. That proves a lot.
I would start at the breaker panel, and tighten both the hot wire on the breaker, and the neutral wire on the white connection buss. Do them all if you can, it's a good idea. Obviously, pull the power before doing that.
Heavy wires go to the A/C, then a lighter wire goes to the thermostat and comes back and picks up relays to permit motors to run. If you can troubleshoot electrically, it's just a matter of elimination to see what is wrong.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel