Ok first VISUALLY inspect the jacks to insure no SLIVER is showing above the pads. (If there is hit the RETRACT ALL again and if it still shows take another jack (like a bottle jack) Center under pad and lift a bit and hit all retract.
If that does not do it or of no silver showing you got to find the tank, and the tank is.. Connected to the pump.. So have parther operate jacks while you do the walk around and use the ears to locate pump
Workhorse Custom Chassis it was front and center under hood behind .. well there is no bumper but that's what it's behind.