Ionic: Send Push Notifications via firebase from device to device : Sending doesn't work from iOS

Question

Sending push notifications from device to device works fine with this code, but only on Android and from a browser.

For some reason this does not work on iOS, no matter if I use the postData object or the stringified payload. Any ideas why?

import { HttpClient } from '@angular/common/http';

public sendPushNotificationToToken(token: string, pnServerKey: string, message: string, userId: number): Observable<any> {

    const firebaseUrl = "https://fcm.googleapis.com/fcm/send";

    const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        'Authorization': 'key=' + pnServerKey
      })
    };

    const postData = {
      'to': token,
      'priority':'normal',
      'notification': {
        'title': message,
        'message': message,
        'userId': userId
      },
    };

    return this.http.post(firebaseUrl, postData, httpOptions);

Answer 1

The only way to solve this was to use "@ionic-native/http/ngx" instead of '@angular/common/http'. Still don't see why the google Server refused to accept my payload.