Manual mode not working
 

So I'm looking over my truck as its having issues and the Manual Mode isn't lighting up, showing what gear I'm in or the line underneath it to show its selected. It had started after we got some snow rain mix and the truck wasn't shifting properly. I've noticed that if I have the battery disconnected for about half hour then reconnect and go to start the truck and put it in Manual right away it will light up and show the 1 beside it for a split second then disappear. Anyone have this issue before or know where to look? I've checked the wires from the gear shift in the steering column and they appear to be fine, so does the connections and been looking through wires seeing if any were frayed/ broke and no luck yet, still searching. Any help on where I could look next would be appreciated. Haven't had any luck googling it either.
It's a 2013 Gmc Sierra 1500 5.3l 6l80e transmission