Electric

You do not give enough details to give a proper answer to you but generally the outlets only work when there is input to the trailer from the generator or shore power. You do not state if you have a battery bank and inverter so the above is the best answer to your question with the info given.

Some good reading to introduce you to the 2 different electrical systems in your camper.

12 Volt side of life part 1 

12 Volt side of life part 2 

A bit over simplified.....

Electricity comes in two flavors:

 - AC: Alternating Current: This is the power you have in your house and the outlets that look like the ones in your house. It's generally runs around 120 volts but 60 times per second, it reverses direction. Usually, you get AC from plugging the RV into a shore power pedestal or your generator puts out AC.

 - DC: Direct Current: This is what your batteries put out when you call on them. It generally runs around 12 volts and stays in the same direction. Your car starter for example runs on DC. 

There are devices in your RV that run on AC and those that run on DC.

 - All RVs have a battery charger (aka: Converter). This takes AC and converts it into DC for direct use and to recharge the battery.

 - A small percentage of  RVs have an inverter. This takes DC and coverts it to AC, so that you can use AC while disconnected from an AC source. Of course, it uses up the battery power, so it's limited in what it can run and for how long. 

My bet is you don't have an inverter, so when you shut down the generator and are not plugged in, there is no source for AC power and thus your outlets don't work.

The outlets are not 12 volt powered. One would need to add an inverter to have power without the generator or shore power.

Newbie hit and run post.