onAppEvent was not triggered

[luatnd]

I try to log the event on both iOS and Android, but onAppEvent() has never been triggered.

<PublisherBanner
        onAdLoaded={this.onAdLoaded}
        onAdFailedToLoad={this.onAdFailedToLoad}
        {...props}
        onAppEvent={this.onAppEvent}
      />

 onAppEvent = (e) => {
    console.log('{onAppEvent} e: ', e);
 }

I'm using "react-native-admob": "^2.0.0-beta.6",
I read through the docs (https://developers.google.com/ad-manager/mobile-ads-sdk/android/banner#app_events) and read the source code, nothing seems wrong.

How can I get onAppEvent to be triggered?