Does this have the kickdown switch at the gas pedal? You have power TO the switch, do you have power THROUGH the switch when the gas pedal is stomped?
You likely need to re-set the initial position of the switch, since "pushing the switch-bar forward" is exactly what you do NOT want to do. You need to move the switch-bar REARWARD as installed, THEN push the gas pedal to WFO. You'll hear the "ratchet" of the switch parts self-adjusting as the pedal is close to WFO.
Sometimes the switches get sticky due to old grease. I pull 'em apart for cleaning, inspection, and fresh lube.
With the ignition "on", you should be able to hear the trans kickdown solenoid click when the pedal is pumped. No clicking = failed electrical including the adjustment; or a failed solenoid.
It's moderately common for the gas pedal to bend so that the carb does not truly go to WFO, and the kickdown switch doesn't get fully activated. You can bend the metal of the pedal assembly to regain the lost motion, but it'll just bend again if the throttle cable or carb linkage is stiff. Best to weld-in a reinforcement after verifying that there's no excess force required at the cable or carb(s).