Can't get the frog to move, even though the code is correct and connected to the prefab itself.

private Animator playerAnimator;
private float moveHorizontal;
private float moveVertical;
private Vector3 movement;
private float turningSpeed = 20f;
private Rigidbody playerRigidbody;

// Use this for initialization
void Start () {
    playerAnimator = GetComponent<Animator> ();

    playerRigidbody = GetComponent<Rigidbody> ();

}


// Update is called once per frame
void Update () {
    moveHorizontal = Input.GetAxisRaw ("Horizontal");
    moveVertical = Input.GetAxisRaw ("Vertical");

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

void fixedUpdate () {
    if (movement != Vector3.zero) {

        Quaternion targetRotation = Quaternion.LookRotation (movement, Vector3.up);

        Quaternion newRotation = Quaternion.Lerp (playerRigidbody.rotation, targetRotation, turningSpeed * Time.deltaTime);

        playerRigidbody.MoveRotation (newRotation);

        playerAnimator.SetFloat ("Speed", 3f);
    } else {
        playerAnimator.SetFloat ("Speed", 0f);
    }
}