Google admob video shown only once for session

I Have another problem with ads, in my app can be shown 2 ads. 1 banner that is loaded when the app starts, which is always shown and works fine. There is another ad, which is a video ad shown to the player by clicking a "show add button for bonus life" after a "GAME OVER". It works only one time, after the first match, no ads are shown if the player try to get his bonus life after a game over... Any suggestions? I will paste the code:

Please consider the #android version only

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using admob;
 
 public class AdManager : MonoBehaviour {
 
     public static AdManager Instance{set;get;}
     public static int inizializzato = 0;
     public string bannerId;
     public string videoId;
     public static int bonuslife = 1;
 
     private void Start(){
 
         if (inizializzato == 0){
         Instance = this;
         DontDestroyOnLoad(gameObject);
         inizializzato = 1;
 
             #if UNITY_EDITOR
             #elif UNITY_ANDROID
             Admob.Instance ().initAdmob(bannerId,videoId);
             Admob.Instance ().setTesting(true);               //EDITOR MODE
             Admob.Instance ().loadInterstitial ();
             #endif
 
         }
         else
         {
             return;
         }
     }
 
     public void showBanner()
     {    
         #if UNITY_EDITOR
         Debug.Log ("BannerAd");
         #elif UNITY_ANDROID
         Admob.Instance ().showBannerRelative (AdSize.Banner, AdPosition.BOTTOM_CENTER, 0);
         #endif
     }
 
     public void showVideo()
     {
 
         //if(bonuslife == 1){
         #if UNITY_EDITOR
         Debug.Log ("VideoAd");
 
         if(bonuslife == 1){
         bonuslife = 0;
         Application.LoadLevel("PlayZone");
         }
         else{
         Application.LoadLevel("DefinitiveGameOver");
         }
         #elif UNITY_ANDROID
 
         if (Admob.Instance ().isInterstitialReady () && bonuslife == 1)
         {
             Admob.Instance ().showInterstitial ();
             Admob.Instance ().initAdmob(bannerId,videoId);
             Admob.Instance ().loadInterstitial ();
             bonuslife = 0;
             Application.LoadLevel("PlayZone");
         }
         else {
 
         if(bonuslife == 0){
         Application.LoadLevel("DefinitiveGameOver");
         }
         else{
         Application.LoadLevel("NoVideoGameOver");
         bonuslife = 0;
         }
         }
         #endif
         //}
     }
 }
 

OLD QUESTION - SOLVED BY DELETING ALL THE MANIFESTS AND CREATING A CUSTOM NEW ONE I'm just adding the ads in my game because I finished it. I was following this tutorial: https://www.youtube.com/watch?v=khlROw-PfNE because it's the first time that I use Google Admob, I followed the video but I have a lot of errors while building the game. So i google a lot and I decided to download the last version of the plugin from the site. But I dont know, it seems that all changed, for example "using AdMob now is replaced with "using GoogleMobileAds" I replaced that and now nothing works. The code seems completely wrong... Does anyone has an update tutorial? or can check my code? thanks