Perhaps some questions on how you are set for testing and what level experience may help speed things along.
Do you use a meter for testing and feel okay with that? How about reading drawings with some guidence? Any experience with the areaof techie stuff?
Meantime, i thinkI have found the correct drawingfor th e110AC on your Rvand I did a couple snips of the area mentioned as a way to pass along some ideas, if that is an area you are used to.
It reads somewhat like a terrible confusing road map if not looked at one before but actually something that can make some sense even if totally new.
First you have a main breaker panel where one breaker feeds a set of wires going an inverter panel. That second panel then has breakers feeding the various circuits which will work through the inverter.
First the main with the breaker involved in the inverter feed.
Click these snips to bring them up larger or go direct to the last sheet of this drawing.
https://www.winnebago.com/Files/File.../000211600.pdf
Then the second panel with the inverter breaker and smaller breakers for different items.
Since the GFCI will not reset, I suspect that is because it is not getting any 110AC power to it. That will keep it from resetting.
It needs a check of each of these brerakers, turned fully off and then fully on to assure they are actually set right as they can sometimes be tripped but not look like it.
Check the bathroom GFCI plug to find there is AC into the RV for sure? It is on a different leg from other things.
A voltmeter to check for voltage on other circuits would be good if one is onhand.
Do a bit of testing to see what other items are/ are not working,perhaps?