the referenced script (Unknown) on this Behaviour is missing Unity 2D

soo I wrote a script that I saw on youtube by a channel called Jackson Academy and when I finished writing it, unity gave me a warning/error message “the referenced script (Unknown) on this Behaviour is missing”, I tried out all the answers and nothing worked… here’s my code:

public class PlayerController : MonoBehaviour
{
    public Rigidbody2D rb;
    public float movementSpeed;
    public float jumpHeight;
    private bool grounded;
    public Transform groundCheck;
    public LayerMask groundLayer;

    private void Update()
    {
        grounded = Physics2D.OverlapCircle(groundCheck.position, .2f, groundLayer);
        rb.velocity = new Vector2(Input.GetAxis("Horizontal") * movementSpeed * Time.deltaTime, rb.velocity.y);
    }
}

and here’s the warning:alt text

PLEASE HELP!!!

Check if your file name matches the class name