"Hostname match not found" error in firebase phone authentication(with ionic)

I'm trying to combine "firebase phone authentication" with ionic.

but, stuck in one question.

I keep getting "Hostname match not found" error from

.catch(function (error) { 
  console.log("error! : " +  error); 
});"

of login.ts(below)

import { Component } from '@angular/core';
import { IonicPage, NavController, AlertController } from 'ionic-angular';

import firebase from 'firebase';

@IonicPage()
@Component({
   selector: 'page-login',
   templateUrl: 'login.html',
})

export class LoginPage {
  public recaptchaVerifier:firebase.auth.RecaptchaVerifier;
  constructor(public navCtrl: NavController, public alertCtrl: AlertController) {}

  ionViewDidLoad() {
    this.recaptchaVerifier = new firebase.auth.RecaptchaVerifier('recaptcha-
    container');
  }

  signIn(phoneNumber: number){
    const appVerifier = this.recaptchaVerifier;
    const phoneNumberString = "+" + phoneNumber;

    firebase.auth().signInWithPhoneNumber(phoneNumberString, appVerifier)
      .then( confirmationResult => {

        let prompt = this.alertCtrl.create({
        title: 'Enter the Confirmation code',
        inputs: [{ name: 'confirmationCode', placeholder: 'Confirmation Code' }],
        buttons: [
          { text: 'Cancel',
            handler: data => { console.log('Cancel clicked'); }
          },
          { text: 'Send',
            handler: data => {
               confirmationResult.confirm(data.confirmationCode)
                 .then(function (result) {

                 }).catch(function (error) {

                 });
            }
          }
        ]
     });
     prompt.present();
   })
   .catch(function (error) {
      console.log("error! : " +  error);           //   <------------The place that informs this error.
   });
 }
}

this error occurred shortly after reCAPTCHA solved

Why does this happen?

--Initializing Firebase

--login.html