If they charge from engine but not from shore then the converter is toast or at least the fuses that are part of the converter are.
Minor exception in some cases.. SO I'll add one qualifier
This is PROVIDED the interior 12 volt lights work with full batteries. (Otherwise it could be the battery disconnect)
Converters come in 2 flavors for this post: Integrated (part of power distribution panel) and stand alone. On Integrated units there are usually 2 30 amp fuses, usually on the right end of the fuse board. KEY word is USUALLY.
On Stand Alone there will be 1-2 or 3 depending on the converter, and they will be somewhere on the converter itself.