Facebook Native not working

Ionic Framework ionic-v3
#1 
<ion-header>
  <ion-navbar>
    <ion-title>
      Ionic Blank
    </ion-title>
  </ion-navbar>
</ion-header>

<ion-content padding>
  <button ion-button full (click)="loginWithFB()">Login!</button>
  <ion-card *ngIf="userData">
    <ion-card-header>{{ userData.username }}</ion-card-header>
    <img [src]="userData.picture" />
    <ion-card-content>
      <p>Email: {{ userData.email }}</p>
      <p>First Name: {{ userData.first_name }}</p>
    </ion-card-content>
  </ion-card>
</ion-content>


import { Component } from '@angular/core';
import { Facebook, FacebookLoginResponse } from '@ionic-native/facebook';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {

  userData = null;

  constructor(private facebook: Facebook) {

  }

  loginWithFB(){
    this.facebook.login(['email', 'public_profile']).then((response: FacebookLoginResponse) => {
      this.facebook.api('me?fields=id,name,email,first_name,picture.width(720).height(720).as(picture_large)', []).then(profile => {
        this.userData = {email: profile['email'], first_name: profile['first_name'], picture: profile['picture_large']['data']['url'], username: profile['name']}
      })
    })
  }

}

First time works, second time shows This app has no android key hashes

cordova-plugin-console 1.0.5 "Console"
cordova-plugin-device 1.1.4 "Device"
cordova-plugin-facebook4 1.9.1 "Facebook Connect"
cordova-plugin-splashscreen 4.0.3 "Splashscreen"
cordova-plugin-statusbar 2.2.2 "StatusBar"
cordova-plugin-whitelist 1.3.1 "Whitelist"
ionic-plugin-keyboard 2.2.1 "Keyboard"
#2

add key hashes to your Faccebook app

#3

I am still testing the app. Should I add hashes after is for prod ?

#4

you must add, it is required

#5

just copy that hash key which is showing on facebook login in your facebook developer account for testing and you have to add other hash key for production