WASD won't work

So I was doing the roll a ball project, and just did my code for the player movement and I tried to move with my WASD keys but I couldn't. I looked at the input manager and my keys were WASD. I Here is my code. using System.Collections; using System.Collections.Generic; using UnityEngine;

public class PlayerController : MonoBehaviour {

 public float speed;

 private Rigidbody rb;

 void start ()
 {
     rb = GetComponent<Rigidbody> ();
 }
 void fixedupdate ()
 {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

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

     rb.AddForce (movement * speed);
 }

} I am puzzled why this won't work. Any help would be helpful. :D