Pmccomas, as Tumblebug said, you may have tripped the garage breaker. One troubleshooting technique that works well is to start at the source and work toward the problem. In your case, check that the garage outlet is actually providing power by plugging something else into it. If that item works, then go to the mpg. Do any of the outlets work? If not, then the problem is between the garage outlet and the mpg. Has your power cord become detached? For that matter, is it still there? You wouldn't be the first person to have had a power cord stolen for the little bit of copper in it.
I'm guessing (and that's all it is) that your breaker in the garage has tripped. If weather permits, get an extension cord and plug the microwave by itself into an outlet that you know works, preferably the same one you were using for the whole camper. I'm guessing that the microwave will trip the breaker. If it doesn't, and a hundred-watt lightbulb to it, and see what happens.
Of course, you have checked that there is nothing else on that circuit, haven't you? Don't ask how I know to ask that question!