googleads-mobile-unity: Instantly Crashs on "Initialization" for "InterstitialAd" & "RewardVideoBasedAd"

Thank you so much for taking your valuable time to take a look into the following issue.

I have attached the “unityPackage” by which you can test it on your editor & device. Also, the following script shows how it was ported to physical device for testing.

UnityPakage : https://drive.google.com/open?id=0B-YWb5BzJ1ZeSkFyN2VKTGtqY0E “Video” showing crash report : https://drive.google.com/open?id=0B-YWb5BzJ1ZeVWRfYlpjdG4zd2c DeviceID : https://drive.google.com/open?id=0B-YWb5BzJ1Zed29yT1NJcnl4cEU

Additional Information:

Unity Version ; 2017.1.0f3
Admob SDK  : Google Mobile Ads Unity Plugin - v3.8.0
Android Device : Asus Zenfone - 5
OS Version : 5.0 (Lolipop)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using GoogleMobileAds;
using GoogleMobileAds.Api;

public class TestScript : MonoBehaviour {

	InterstitialAd interstitial;

	private string debugMessege;
	// Use this for initialization
	void Start () {

	}
	
	private void mInitializeInterstetialAd(){

		debugMessege = "Before Initialization"; 

		#if UNITY_ANDROID
		// InterstitialAd testID from admob
		string adUnitId = "ca-app-pub-3940256099942544/1033173712";
		#elif UNITY_IPHONE
		string adUnitId = "INSERT_IOS_INTERSTITIAL_AD_UNIT_ID_HERE";
		#else
		string adUnitId = "unexpected_platform";
		#endif


		// Initialize an InterstitialAd.
		interstitial = new InterstitialAd(adUnitId);
		debugMessege += "\nInterstitialAd Initialized";

		// Create an empty ad request.

		AdRequest request = new AdRequest.Builder()
		.AddTestDevice(AdRequest.TestDeviceSimulator)
		.AddTestDevice("A1803A2F089A97C5")
		.AddTestDevice("357996068713245")
		.Build();

		debugMessege += "\nAfter AdRequest";

		// Load the interstitial with the request.
		interstitial.LoadAd(request);
		debugMessege += "\nLoad InterstetialAd";
	}

	void OnGUI(){

		float mHeight = Screen.height / 10.0f;

		if (GUI.Button (new Rect(0.0f, 0.0f, Screen.width, mHeight),"Initialize")) {

			mInitializeInterstetialAd ();	
		}

		if (GUI.Button (new Rect(0.0f, mHeight, Screen.width, mHeight),"ShowAd")) {
			
			if(interstitial.IsLoaded())
				interstitial.Show ();
		}

		GUI.Label (new Rect (0.0f, mHeight * 2, Screen.width, mHeight * 2), debugMessege);
	}
}