This is a good starting point...
12 volt Side of Life part 1
The 12volt Side of Life (Part 1)
12 volt Side of Life part 2
The 12volt Side of Life Part 2
Some of the information is a little dated, but it is still pretty good.
Shore power provides power to AC, microwave, and various outlets. Do any of these things work? If they do then move on to 12 volt side. If not look for breakers tripped (switch "off", then back "on"). External power cord connector may be loose. Pedestal breaker may be "off".
Shore power also supplies power to a converter/charger. The converter should power 12 volt lights, fans, controller for water heater, controller for refrigerator, and other 12 volt things. Do any of these things work? If so, continue for individual appliances that do not work.
Many RV's have a "salesmen switch". It will be near the entry door. It turns most 12 volt appliances "off". Turn it "off", then back "on".
Check fuses. Mine has 30 amp and 40 amp main fuse. They may be in a main fuse panel. Sometimes you can see they are blown, sometimes not. Get replacements and substitute as a test. It is always good to have spare fuses. You can also remove and ohm test across the blades or measure voltage across the fuses. Voltage should always be zero.
Individual 12 volt appliance may have a dedicated circuit. Check fuses for that circuit.
There are many possible wiring situations. Please post make and model of converter/charger. It is also possible you have an inverter and/or a transfer switch. Make and model gets you better advice.