The first time this happened to me I did the same thing. Pushed the reset button on the GFI outlet and even removed it and measured for voltage. I had already checked all the circuit breakers in the main panel and didn't realize that the inverter also had a couple. Bought a new outlet and replaced the one that wasn't working....like you, it still wouldn't work.
Finally someone here on rv.net told me about the cb on the inverter. Yep, that was the problem. So, ever since then, whenever someone here writes in stating this type of problem, the first thing I do is tell them about the cb on the inverter. 9 times out of 10, that's the problem.
Ron