Tail lights on an 04 Dodge ram 2500 Crue cab four wheel drive

I have a 2004 Dodge ram 1500 slt
Crue cab four wheel drive and my
husband tried wireing up his car
haleing trailer to it and he got all the
lights to work but the tail lights what
would cause the turne signals and
break lights and emergancey flashers
to work but not the tail lights because
they all work on his 88 Chevy s10