Question Problem with animations

Hi guys, I created a simple transition influenced by a parameter called isWalking, as you can see in the video, the real problem is that I can't get an animation change going from the "idle" state to "walk". I can get a change of animation only if i set "isWalking" as true before the runtime.

I also coded the transition, setting "isWalking" as true when I press "w", the parameter sets to true, there is a change of state, from "idle" to "walk" but there is no change of animation

//other scripts...
void Update()
{
if(Input.GetKey("w"))
{
transform.Translate(speedPlayer * (Vector3.back * Time.deltaTime));
animator.SetBool("isWalking", true);
}
//other scripts...
}