Ionic3 admob not displaying

I am trying from last 7 days to run Google AdMob in Ionic 3 application. Steps I followed as shown here

By using below code, the ads is not displaying! I have followed this tutorial.

Current issue: No ads displaying and Not getting any error!

In component code

    ....
    ....
    constructor(public storage: Storage, public navCtrl: NavController, private platform: Platform,public admob:AdmobFreeService) {  
        this.platform.ready().then(val => { 
          this.admob.BannerAd(); 
        });

In service

   import { Injectable } from "@angular/core";
    import {
      AdMobFree,
      AdMobFreeBannerConfig,
      AdMobFreeInterstitialConfig,
      AdMobFreeRewardVideoConfig
    } from '@ionic-native/admob-free/ngx';
    import { Platform } from 'ionic-angular';
    
    
    @Injectable()
    export class AdmobFreeService {
     
      constructor(
        private admobFree: AdMobFree,
        public platform: Platform
      ) {
    }
 
    
      BannerAd() {
        let bannerConfig: AdMobFreeBannerConfig = { 
          autoShow: true,
          id: "ca-app-pub-4622639730805786/6571035695"
        };
        this.admobFree.banner.config(bannerConfig);
        this.admobFree.banner.prepare().then(() => {
          // success
          this.admobFree.banner.show(); 
        }).catch(e => alert(e));
      } 
    }