Sometimes with two chargers on the battery bank, one won't start with the other on. Eg, with a portable smart charger and the converter, turn off the converter, get the portable going and then turn the converter on.
I don't know what the issue is here, but you could try to get one running and then turn the other on and it might stay on. If not then try the other one first and then turn on the second one. Never know, worth a try. Idea is they are probably not exactly the same voltage by a tiny amount. You want to get the lower voltage one running before turning on the higher voltage one
