Do you have an inverter? What kind?
Many times when they install an inverter they do bond ground to neutral, this will trip a GFCI... In some cases (IE: My prosine 2.0) there is a proper way to do it that will prevent this from happening, but if you do it WRONG, it happens anyway (I know, did it both ways).
Also, Here is the tribble shoot.
First turn off every breaker INCLUDING the mains.
I suggest plugging in a trouble lamp (Drop cord lamp) and having it inside the RV so you can see it. Have the light on
Plug in the RV (Same GFCI duplex.
Does the light stay on or does it trip.. If it trips post and stop reading.
Now turn on the mains.. Does it trip.. See above instructions.. NO continue
Turn on one branch, Then another, till it trips
now turn off the last one and reset, then continue leaving the one that tripped it off.
When you are done you will have one, or more, breakers OFF.
Find out what devices those breakers feed, and POST.
Home is where I park it!