Laravel Echo + Pusher subscription_error on private channel

I can't manage to get echo and pusher working when using private channels, googled for two days and found nada.

What seems to be happening is some sort of problem with the authentication (I'm using Laravel basic Auth) cause I can subscribe to public channels

routes/channels.php

Broadcast::channel('private-ci-received-{userId}', function ($user, $userId) {
    return (int) $user->id === (int) $userId;
});

Broadcast::channel('private-ci-received-{toUserId}', function ($currentUser, $toUserId) {
    return true;
});

bootstrap.js

import Echo from 'laravel-echo'

 window.Pusher = require('pusher-js');

 window.Echo = new Echo({

     broadcaster: 'pusher',
     key: process.env.MIX_PUSHER_APP_KEY,
     cluster: process.env.MIX_PUSHER_APP_CLUSTER,
     logToConsole: true,
     encrypted: true,
 });

default.blade.php(main layout file)

        Pusher.logToConsole = true;
        Echo.logToConsole = true;

        Echo.private('ci-received-{{ Auth::user()->id}}')
            .listen('.CIReceived', (e) => {
                console.log(e);
            });

What get printed on the console is :

Pusher : No callbacks on private-ci-received-1 for pusher:subscription_error

It's a pretty generic error, then for debug purposes I tried to bind the error using Pusher (not laravel echo)

var pusher = new Pusher('MYSECRETAPPKEYHERE', {
            cluster: 'us2',
            forceTLS: true
        });

        var channel = pusher.subscribe('private-ci-received-1');
        channel.bind('pusher:subscription_error', function(data) {
            console.log(data);
        });

console.log(data) output

JSON returned from webapp was invalid, yet status code was 200

The default authEndPoint is /broadcasting/auth IIRC I think it expects to return a JSON but instead it returns the HTML CODE from my page.

Those routes are created by the framework itself and from what I've read Laravel echo and Laravel Auth should work great together without much fiddling.

My .env file is correct i'm using pusher as broadcast driver and BroadcastServiceProvider is properly uncommented.

Can anyone shed a light in the matter? Thanks