Facebook Native not working

<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"

add key hashes to your Faccebook app

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

you must add, it is required

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