There is a chance the battery was reinstalled backwards. On many Crossroads, the Black cable is Positive, and the White is Negative and is chassis ground. Kind of like house wiring.
Barring that, it's possible your trailer battery was very dead. So dead that when the truck was in the circuit, the draw was too heavy and blew something, hopefully just a cheap fuse. Bring the TT battery home and charge it up if possible. Check your truck for a blown trailer tow fuse. There may be several.
Marty and Martha
2015 Z-1 211RD
2012 Nissan Titan