Admob Video ad won't show on android device

using UnityEngine; using UnityEngine.SceneManagement; using UnityEngine.UI;

public class BallScript : MonoBehaviour {

public Vector2 startForce;

static int times = 0;

public Text goverText;

public Vector3[] positions;

public Rigidbody2D rb;

void Start() { int randomNumber = Random.Range(0, positions.Length);

transform.position = positions[randomNumber];

times = PlayerPrefs.GetInt("Text:", times);

rb.AddForce(startForce, ForceMode2D.Impulse);

}

void Update() {

PlayerPrefs.SetInt("Text:", times);

goverText.text = "Text:" + times.ToString();

}

void OnCollisionEnter2D(Collision2D other)

{ if (other.gameObject.name == "wall_bottom") {

times++;

if (times == 14) { AdsManager.Instance.ShowVideo(); }

if (times == 30) { AdsManager.Instance.ShowVideo(); }

if (times == 45) { AdsManager.Instance.ShowVideo(); }

SceneManager.LoadScene("wfvv");

}

}

}