No power after running generator

Check the inverter, it likely has a type of breaker or on/off switch.

How did you check pedestal? Did you reset pedestal circuit breakers, by moving the handle to off with slight pressure then turning back on?
Did you reset all circuit breakers in 120 volt distribution panel. Turn on breakers applying light pressure toward off, then turn back on.
Was shore power cord disconnected when running the genset? If so the transfer switch could be stuck. Disconnect from shore power, restart genset, then shut it down, plug in shore power.
Blown fuse on transfer switch control circuit.
Is there any 120 volt items working in the rig? Micro wave? Air conditioner/

automatic transfer switch? By the way, do you think your sister would appreciates you calling her rig a piece of garbage? I know if my sister said that to me, well let's say we would not be talking to each other for a while

However, this info should be contained the manuals for the RV.
My thoughts are it has a ATS allowing the switching from shore power to generator without moving plugs. Normally, there is a 30 second delay when switching.

Did you check the breaker on the generator itself? It's on the lower right side of the gen.

I have a 2007 Georgetown 35 bunkhouse and do not agree with your statement that they are garbage. The onan genset on your sister's is probably the exact same model that every class A gas motorhome comes with. Now, I am not sure about the 2015, but the 2007 does not have an automatic transfer switch. It has a socket in the electrical bay that you plug shore power into when not plugged in at the campground. This socket is powered by the generator. If this is the configuration that your sister has, the first obvious check is to see if the shore power is plugged into this socket.

If that doesn't help, check that there is output voltage from the generator. You can use a meter at the genset itself.

I occasionally have had trouble with the exciter field on my generator losing magnetism. My genset (a generac) actually flashes the field with every startup. I have found that if I do not get generator output voltage, I can stop and start the genset engine a couple of times and it comes back.

Good luck, and tell us what you have found.

Check the GFI, they will sometimes trip when changing power modes. If it won't reset, it has no power to it.

The transfer switch was the problem. Thanks everyone

The OP must clarify problem.
To me, it sounded like they exercised the genset, shut it down and went back onto shore power and have nothing.