[wingnut60]

So you are using only 12volt and it is not plugged in?
The converter ONLY works off 120volt and puts out 12 volt power to charge the battery--the battery runs everything in the trailer that is 12volt. IF you are not plugged in, the converter can't work.
What is sounds like you are doing is just running the battery down after getting it charged. The gen should have provided 120volt to the converter and then it should have charged the battery up some--takes quite awhile to get any good charge out of the converter.
You probably now need to charge the batter again, but it is going to run down again unless you can get the trailer plugged in.
And, if using a gen to charge the battery, it will go better if you also use an automotive battery charger at the same time--won't hurt anything.
Be sure battery connections are both clean and tight. Also, follow the positive lead to see if you have a relay nearby---if so, check for a tiny black reset button on the side of the relay. Push the button in if there is one. If it is present, and not reset, then it is cutting power off to the 12volt items in the trailer.
Hope some of this helps.
Welcome to our forum.
Joe