Just an update.
The problem went away. Think it must have been contact chatter or something that caused the Prog. Ind. EMS to call a frequency error. And now that the contacts have had a chance to "break-in", it's not happening, or not as frequently.
Also, it always takes me a while to get things set up outside. So I plug in the 120VAC, and continue doing other stuff for easily 10 minutes before going inside to check if there's 120VAC power. By then, the EMS has potentially had 10/2 tries to startup, and it has always been successful, even though I didn't kept track of how many attempts it made.
My correspondence with Prog. Ind. was a total waste of time. They kept telling me that since there was an Inverter in the circuit (even though it was turned off) they were not responsible. Nice product but not impressed with customer service. After two emails trying to educate them, I gave up.
