I would open the end of the umbilical and make sure nothing has shorted at the connection screws. Disconnect the battery before opening the umbilical.
If things look corroded around the parking light or battery screw you may have had a high resistance connection between those 2 terminals that blew the fuse and opened that connection at the same time.
If thinks look good I would lift the parking light wire off the terminal and try a fuse between that wire and battery with the battery reconnected. If the fuse blows the problem is in the trailer.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles