The inverter generator has an unbonded or "floating" neutral. That's common among small inverter generators. So, you need to bond neutral to ground if you want to use it with the EMS. There is some debate about whether or not you need to run the EMS with the generator at all. Personally I use it because I think of a generator as just another means of shore power, and the EMS protects the trailer from spikes as well as undervoltage. But, I can see where others have a completely different opinion and consider it unnecessary.
If you want to use the EMS with the Honda eu2200i generator, simply use an N-G Bonded plug inserted in one of the unused receptacles on the generator. The bonded plug is just a regular Edison plug with a wire inside connecting the ground terminal to the neutral terminal. That's all there is to it. There's likely nothing wrong with the generators you returned.
You can successfully run the 11.5K BTU Dometic AC with a single Honda eu2200i. Many people on this forum have done so. In fact, many have done so with the older eu2000, which has even lower output power. The issue is the startup amps the AC uses, which are higher than the running amps. The startup amps come close to exceeding the output power of the generator. Be aware that the output power is also affected by your elevation. The higher you go, the less power the generator will produce. Since you mentioned you have two generators, connecting them together with parallel cables will easily run your trailer's AC, with some power to spare - even at higher elevations. At lower elevations, you'll probably do just fine with one.
I and others have posted in several places on how to make a bonded plug. For more info check out post 16 in this thread:
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