If you are comfortable with electricity and using a voltmeter, I would start with checking the pedastal to make sure you are getting 120 vac from both legs of the 50 amp service. May be missing a hot leg.
If good, then open your breaker box and make sure you are getting the same voltage to both sides of your main two pole breaker, both the input side and the load side. If no power to the input side you may have a bad power cord. If no power to the load side then you may have a bad breaker.
If good, then check to see that you are getting that voltage to all the other AC breakers. If not then you may have a problem in your load center.
If everything still looks good then check all GFCI outlets, although I do not think those were connected to the ACs.