GFCI won't reset

Evanford, I note that you are not electrically knowledgeable, so I will try to give you some starting ideas, despite my chest cold induced stupor! ??. From your description, you have no AC at any outlet in the trailer. Logic would dictate you start at the starting point.....your shore power. I wish you had and could use a Voltmeter, or at least an AC socket tester, but since you don’t we’ll proceed this way. First check your house breaker. Just because a breaker doesn’t look tripped doesn’t mean it isn’t. Manually trip the breaker and then put back ON. You don’t say what you are using for shore power outlet, but if possible plug some known good device into it in place of your trailer cord and confirm you do have AC at that point. I don’t know what your connection to the trailer is, either. If not hardwired, can you check for electricity at the other end of the cord? Can you access whatever interface you have at that end to test? Inside your trailer manually trip ALL AC breakers and reset them.
Given the limitations you are working with, and lack of specifics for me, this is about all I can suggest at the moment.