Magnum Inverter Panel

Try resetting the Magnum itself first. It's been a really long time but I think there is a reset button on it. If not, pull power. Also pull and re-seat the RJ connector on both sides. Tech support will likely tell you to do this anyway, so might as well do it before you pick up the phone.

Call Magnum Energy factory in WA state and give them the error code and they can tell you what is the problem. I understand they have a certified tech in OH and NC . They may have one nearer you. The company and tech in NC are very nice people to deal with.

That would be some sort of a programming error or crash in the little computer that controls the inverter. I suggest you turn it off and disconnect all power (both 120V and 12V) for a period of time and then reconnect to see if that resets it and it starts working. If it has a reset button you can push somewhere, try that first.