1995 f250 dual fuel tanks

I have a 1995 f250 with a 7.3 powerstroke I just had
the bed off to replace the filler and neck and fix the
trailer wiring. Before I took the bed off the front fuel
tank worked perfectly fine and the rear one did not,
I inspected the rear float and even tested it by
moving it up and down and saw the gauge on the
dash work from me moving it. After putting the bed
back on I tested them again and both still work fine,
after starting the truck up for the first time it died
using the front tank and only runs on the rear tank
now (reverse From before having the bed off) the
rear tank reads about a 1/4 of a tank even tho it’s
full and the front tank reads empty when it’s full and
a reminder the front tank worked completely fine
before the bed came off. Any idea to what could
have happened ? I did change the switch on the
dash to a new one and test it before starting the
truck and it worked.