I've assigned many different keys to allow my soldier to run. None of them have worked. I can't get my soldier to run Help.

in GRAw you cannot run, its not included in the game, remember this is a tactical shooter and not a run and gun game.... you can dash to the ground though hitting the prone key.

Normal procedure for PC: button W is walk forward, W + holding down shift is run forward. Same goes for the other directions ofcourse.