AdMob ads showing fine on ios but rarely showing on android emulator

Question

I'm using the following code to display ads on my app with the use of cordova-plugin-admob-free, it is working fine on ios and without issue but when I hop into android, only sometimes will the ad display. Out of 50 launches it has shown only once or twice. I'm testing on an nexus 5x emulator.

  var admobId = platform.is('ios') ? "iosid" : "androidid";

  const bannerConfig: AdMobFreeBannerConfig = { 
    id: admobId, 
    autoShow: true, 
    isTesting: true 
  };

  this.admobFree.banner.config(bannerConfig);

  this.admobFree.banner.prepare().then((e) => { 
    console.log(e) 
  }).catch(e => console.log(e));