No 12v input from battery, 2004 Terry Trailer

Thanks for all of the advice/responses. The positive battery cable goes under the A-frame and immediately up, into the floor of the trailer. I traced it with a tracer and it is unbroken back to the power boards/center and converter. No inline fuse/junction/etc. Googled the manual for the WFCO 45 amp converter and viola! Found 2/30 amp fuses (specifically for reversed polarity) on the "back" of the unit. Access to the fuses was virtually impossible due to where/how it was mounted. Managed to dismount the unit enough to coax the fuses out. Visual and continuity tests indicated they are OK. Even cleaned the ground for the neg. battery cable. At this point I figure the (14 year old) converter is shot. Thanks to all who came to my aid. Wish it had resulted in a better (cheaper) outcome. Stay safe.