Your convertor is dying. This is exactly what mine did when it died.
You have two electrical systems in your coach. The 30 amp 120vac (volts alternating current) power goes to the outlets, a/c, microwave, frig, and powers the convertor. The convertor produces 12vdc (volts Direct current) which pretty much runs everything else. Charges battery, Lights, radio, slide, control voltage for frig, a/c and furnace. (This is why your a/c didn't run when there was no 12v)
You most likely have a WFCO 8955 power center, behind the black cover there should be about 5 standard house breakers, this is your 120vac power distribution. There will also be approx. 10, 12v auto type fuses, these are for your 12 volt power. One of the 120v breakers feeds the 12v convertor, make sure it is not tripped, but you will need a new convertor.
This is what I replaced mine with:
Boondocker Main Board Assembly for WFCO 8955
If you are not electrical savay, I would have someone replace it for you. I did my own, took about 3 hours, but I'm an Electrician.
This is a three stage convertor and you'll find it will maintain your battery much better than the original.