Audio not working on first run of game, but after second run it does

Hi,

In my game I have a television. I have a box collider on it with a trigger. The television screen has a black texture. When I enter the trigger I can turn on the tv and the black texture is replaced by a movie. Everything is working fine. Only the audio is not playing. But is I stop Unity player and run the game again, the audio is working. I didn't try to compile the game to see if the problem is also there. I only tested it inside Unity itself. Every time I restart Unity, on the first run of the game, I have this problem. But every run after the first one, it's working fine. I'm a little afraid that when I compile the game I have this problem. But unlike Unity, when you start the game, you can't use the "play" "pauze" buttons to run the game a second time. If the game is started, it is always a first run.

This is the script I'm using:

 using UnityEngine;
 using System.Collections;
 
 public class tvdoenspelen : MonoBehaviour 
 {
 
 public Material[] myMaterials = new Material[5];
 int maxMaterials;
 int arrayPos = 0;
 bool drawGUI = false;
 bool tvspeelt = false;
 AudioSource audio;
 
 void Start ()
 {
     maxMaterials = myMaterials.Length-1;
         audio = GetComponent<AudioSource> ();
 }
 
 void OnTriggerEnter(Collider col)
 {
     if (col.gameObject.tag == "Player")
     {
         drawGUI = true;
     }
 }
 
 void OnTriggerExit(Collider col)
 {
     drawGUI = false;
 }
 
 void OnGUI ()
 {
     if (drawGUI == true && tvspeelt == false) 
     {
         GUI.Box (new Rect (Screen.width * 0.5f, Screen.height * 0.5f, 200, 22), "Drop op E om TV te kijken");
     }
     
     if (drawGUI == true && tvspeelt == true) 
     {
         GUI.Box (new Rect (Screen.width * 0.5f, Screen.height * 0.5f, 200, 22), "Drop op E om TV af te zetten");
     }
 }
 
 
 void Update ()
 {
     if (drawGUI == true && Input.GetKeyDown(KeyCode.E))
     {
             GetComponent<Renderer>().material = myMaterials[arrayPos];
 
         if(arrayPos == maxMaterials)
         {
             arrayPos = 0;
             tvspeelt = false;
             audio.mute = true;
         }
         else
         {
             arrayPos++;
             tvspeelt = true;
                 Renderer r = GetComponent<Renderer> ();
                 MovieTexture movie = (MovieTexture)r.material.mainTexture;
                 movie.Play ();
                 audio.mute = false;
         }
          
     }  
 
 }
 }

And this is my inspector of my TV screen: