Following tutorial videos yet script doesn't work

Hello senpais,

So I was watching the very first tutorials as I am a beginner at Unity. The video of the rolling ball tutorial (Link at bottom) yet, even though I copied exactly what they showed my "player" did not want to move. Although if I used the script provided under the video it works, even though it seems to be exactly the same... I cannot seem to figure out why and would really appreciate help as I want to continue with Unity. Btw I use Unity 5.5.1f1 and Visual Studio to edit the script

My script

 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);
     } 
 }
 

Video's script

 using UnityEngine;
 using System.Collections;
 
 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);
     }
 }

https://unity3d.com/learn/tutorials/projects/roll-ball-tutorial/moving-player?playlist=17141