The newer 3203BH have the power center under the fridge. The converter should be behind the brown or black panel under the fridge. You will have to remove the panel to gain access to the lower portion.
If the converter is not under the fuse panel, follow the larger cables connected to the right side DC fuse panel. The fuses, not the beakers on the left. Two will be connected to the converter and the other two connect to the battery.
Is he sure be doesn't have the battery disconnect turned off?
If he has inside lights when plugged into shore power the converter is working. If he has lights when plugged in but no lights when he's disconnected from shore power, either the battery is dead or the fuse between the battery and power center is blown.
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