Sounds like there is a bad connection
Somewhere! My guess is a wire or connector is broken inside the E-Z start unit or it could be a broken wire on the truck itself! You can try taking it apart and see what is wrong or you can buy a whole new setup on Ebay for pretty cheap ($15-25).
Or you can do what I did on my TRX Pro and use a glow starter! They work better IMO anyway!