electrical problem

I take it you do not have a Progressive EMS (Electric Magement System) or any surge guard in line with the park pedestal. You should only have 120 volts coming into the RV. Never 220. You more then likely have a converter that converts 120 volts to 12 volts and charges the batteries, and powers all the 12 volt items in the RV. The Microwave is 120 volts not 12volts. Do other 120 items in the RV work? A/C , TVs, hair dryer if plugged in. Did you check the 120 volt breakers in the RV??? Do you have a volt meter are you getting 12.7 volts or better at the battery terminals??? (which will show if the converter is working or not). The converter could be any place mine is in the where all my 12 volt fuses are but a friends is on the wall under the refrigerator. They have a fan on them and sometimes you can hear them running.
And if you got a power surge 120 volt items in the RV could be toast and it would not be the converters fault. The converter only powers 12volt items, lights, water pump,Heater, etc. And these items would work till the batteries ran down.