Firebase - Ionic 4 - verifyPhoneNumber

After install firebase plugin on ionic 4.
Save the google-services.json in the project folder.
Actived the Smartphone login in firebase console.
Test if some function like getToken and other works fine.

I try to use verifyPhoneNumber function like

verifyPhoneNumber(number) {
this.firebase.verifyPhoneNumber(number, 30000).then( res => {
this.msg = JSON.stringify(res);
.catch( error => {
this.msg = error;

The msg ‘JSON error’.
Some can help me, how make it work for login with phone number?