There are two systems in your trailer, and the only interconnection is the converter/charger which changes 120 volts to 12 volts. The 12 volt
side powers your lights, jack, pump etc. If you have a bad battery, an open fuse, or a bad converter charger, plugging the rig into 120 may not do anything.
1. Check the voltage at your battery with an inexpensive digital voltmeter. You can get one for $20 or less. It should be about 12.6 volts with a charged battery.
2. If you have 12 .6 volts at the battery and things still do not work, first clean the battery terminals, then check the big 50 amp fuses to be sure they are OK.
3. When you get the 12 volt
side working again, hook up to 120 Volt power, and be sure the 120 volt circuit breakers are all on. The converter/charger may be plugged into a 120 volt outlet. If it is be sure that outlet is working by plugging something else into it, like a lamp.
4. With your meter on the 12 volt battery, have someone turn the converter/charger circuit on. The voltage on your battery should increase to about 13.5 volts. If it does not, something else is wrong with the converter/charger or wiring or fuses.
Those are some things you can do to start, and report back if you find anything you don't understand. Maybe we can help further.