RV refrigerators require 12V to operate the circuit board whether you're operating the fridge on LP or electric. Is your battery charged, and is the 12V cutoff switch (if there is one) turned on?
The fridge should operate on 120V electric (provided there is also 12V), and plugging it directly into a household outlet will work.
You should be able to loosen the hold-down clamp on the LP tanks and attempt to lift them to see if they feel heavy enough to have at least some LP in them. Also, make sure the valve at the top of the tank is open. You can also test to see if there is any LP coming out by attempting to light the stove. Be patient - if the LP has been turned off for an extended period of time, there may be lots of air in the lines.
Good luck, and keep us posted.