If it was wired wrong and "popped something" then you need to check out all the usual suspects
Since he "Fixed" it.. well it may be hard to detect what he did wrong.
CONVERTER (or inverter/charger if it has one) this is supect #1 SOME of these do not mind 240 volts Most models tend to "Smoke" if you do that.
The joke is electronics runs on magic smoke. you let the smoke out they stop working.
Fridge: The 120 volt heat element and possibly the control board
Water heaters: same as fridge
Air conditioners. Motors and control board
Televison, Radio Sat receiver and MIcrowave more or less round out the list.
NOW: save for the last line.. All this stuff often needs good 12 volts as well so if the converter is toast.. It may not be providing proper power to the rest of it.
Easy way to test converter
Turn it off (You can just flip the main breaker inside the RV or if you know which one the branch) Now turn on lights and/or vent fan. these are 12 volt devices and can run on battery. Lights may be a touch dim or fan run slow. Dont worry about that... Wait a few mintues (one will do) and turn breaker back on. Within seconds (like 5 or less) lights should brighten and fan increase speed. IF THEY DO NOT converter most likely toast.
As for the rest of it... Well That's beyond my ability to tell you now to test it.