Sounds like either the converter breaker is turned off, blown fuse to the battery from the converter (there are two) or the converter is bad.
Easiest way to check is to plug the trailer in to house power, make sure all the breakers in the trailer are on and check the voltage at the battery. Anything under about 13.5 volts DC means no power getting to the battery to charge it up. The fact that the microwave was on and the lights were dead says there is zero output from the converter. So fuses or bad converter or possibly a bad connection. Time for the dealer to step up and fix it ASAP.