Being it is a hydro drive ... The hydro is belt driven that moves the oil thru the drive to move the wheels .
You have changed the belt and you have the same issue . Check the hydro oil level . Rare that it drops down unless you heated it up with dead grass around it . I see more cub cadets and simplicity at work . I have a LT1000 that will not die .
If the belt is on the wrong side of the tensioner you'll be stuck rolling . Double check your brake and hydro pedal for binding - very common in cubs .