I've had to replace two of these since last July due to shorting out internally. It will pass shore power through it when plugged in, but will not provide inverter power. There is a procedure to check it out (call Xantrex). After checking it out and definitively identifying the problem, Thor Customer Service was very good about sending me replacements. It is known that there was a bad batch of the XM 1800 inverters.
2018 Thor Miramar 35.3
2012 Jeep Liberty
5 Star Tuner, Blue Ox, Towtector