Space Shooter Movement Script Not Working

Unity Engine
1

Currently I am working on the Space Shooter Tutorial and the script I wrote is not working. When I removed the script and used the one from the finished game, the ship moved, but when I copied the movement code into my script, the ship failed to move.
My Code:

using System.Collections;
using UnityEngine;

public class PlayerController : MonoBehaviour
{
    public float speed;

   
    void fixedUpdate ()
    {
        float moveHorizontal = Input.GetAxis("Horizontal");
        float moveVertical = Input.GetAxis("Vertical");

        Vector3 movement = new Vector3(moveHorizontal, 0.0f, moveVertical);
        GetComponent<Rigidbody>().velocity = movement * speed;
    }
}

Finished Code from Developers:

using UnityEngine;
using System.Collections;

[System.Serializable]
public class Done_Boundary
{
    public float xMin, xMax, zMin, zMax;
}

public class Done_PlayerController : MonoBehaviour
{
    public float speed;
    public float tilt;
    public Done_Boundary boundary;

    public GameObject shot;
    public Transform shotSpawn;
    public float fireRate;
    
    private float nextFire;
   
    void Update ()
    {
        if (Input.GetButton("Fire1") && Time.time > nextFire)
        {
            nextFire = Time.time + fireRate;
            Instantiate(shot, shotSpawn.position, shotSpawn.rotation);
            GetComponent<AudioSource>().Play ();
        }
    }

    void FixedUpdate ()
    {
        float moveHorizontal = Input.GetAxis ("Horizontal");
        float moveVertical = Input.GetAxis ("Vertical");

        Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
        GetComponent<Rigidbody>().velocity = movement * speed;
       
        GetComponent<Rigidbody>().position = new Vector3
        (
            Mathf.Clamp (GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax),
            0.0f,
            Mathf.Clamp (GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
        );
       
        GetComponent<Rigidbody>().rotation = Quaternion.Euler (0.0f, 0.0f, GetComponent<Rigidbody>().velocity.x * -tilt);
    }
}

I have used both under the same conditions yet my code fails to work.

2

'F’ixedUpdate you need the capital

3

ok thanks