Animator is not playing a Playable UnityEngine.Animator:SetFloat(String, Single)

private Animator playerAnimator;
private float moveHorizontal;
private float moveVertical;
private Vector3 movement;
private float turningSpeed = 20f;
private Rigidbody playerRigidbody;
[SerializeField]
private RandomSoundPlayer playerFootsteps;



// Use this for initialization
void Start () {

    // Gather components from the Player GameObject
    playerAnimator = GetComponent<Animator> ();
    playerRigidbody = GetComponent<Rigidbody> ();

}

// Update is called once per frame
void Update () {

    // Gather input from the keyboard
    moveHorizontal = Input.GetAxisRaw ("Horizontal");
    moveVertical = Input.GetAxisRaw ("Vertical");

    movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

}

void FixedUpdate () {

    //If the player's movement vector does not equal zero...
    if (movement != Vector3.zero) {

        //...then create a target rotation based on the movement vector...
        Quaternion targetRotation = Quaternion.LookRotation (movement, Vector3.up);

        //...and create another rotation that moves the current rotation to the target rotation...
        Quaternion newRotation = Quaternion.Lerp (playerRigidbody.rotation, targetRotation, turningSpeed * Time.deltaTime);

        //...and change the player's rotation to the new incremental rotation....
        playerRigidbody.MoveRotation(newRotation);

        //....then play the jump animation
        playerAnimator.SetFloat ("Speed", 3f);

        //...play footsteps sound.
        playerFootsteps.enabled = true;         

    } else  {

        //Otherwise, don't play the jump animation
        playerAnimator.SetFloat ("Speed", 0f);

        //...Don't play footsteps sounds
        playerFootsteps.enabled = false;

    }
}