How to fix missing behavior,How do I fix The reference script on this "Behavior (Game Object 'Player') is missing" and "Behavior is missing!"

Questions & Answers
1

Only one object has a script. What do I do? I followed the tutorial on the Roll a Ball game, but it didn’t work for me. I also tried other scripts, but none of them work! I can get into play mode, I just can’t move at all.

2

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);

	}
}