Socialite Facebook Client error: 400

Hi everyone,

I'm trying to implement Facebook login using Socialite, was able to get the Google login working but for some reason, I keep getting a Client error: 400 when trying to login with Facebook.

So far, this is what I did:

• Updated all packages via composer update (just in case)
• Laravel version is 5.1.4
• Socialite version is 2.0.7
• guzzlehttp/guzzle version is 6.0.1

on my config/services.php file I have the following:

'facebook' => [
    'client_id' => env('FACEBOOK_APP_ID'),
    'client_secret' => env('FACEBOOK_APP_SECRET'),
    'redirect' => env('FACEBOOK_REDIRECT')
],

on my .env file, I have the following:

FACEBOOK_APP_ID=(the App ID under Settings > Basic > App ID)
FACEBOOK_APP_SECRET=(the App ID under Settings > Basic > App Secret -- the one you need to enter your password to see it --)
FACEBOOK_REDIRECT=http://app.192.168.10.10.xip.io/facebook/callback

my routes files looks like this:

Route::group(['as' => 'auth::'], function() {
    Route::get('facebook/login', ['as' => 'facebook-login', 'uses' => 'Auth\AuthController@redirectToFacebook']);
    Route::get('facebook/callback', ['as' => 'facebook-callback', 'uses' => 'Auth\AuthController@handleFacebookCallback']);
    Route::get('facebook/deauthorize', ['as' => 'facebook-deauthorize', 'uses' => 'Auth\AuthController@handleFacebookCallback']);

    Route::get('google/login', ['as' => 'google-login', 'uses' => 'Auth\AuthController@redirectToGoogle']);
    Route::get('google/callback', ['as' => 'google-callback', 'uses' => 'Auth\AuthController@handleGoogleCallback']);
});

and on my AuthController, redirectToFacebook and handleFacebookCallback methods:

    public function redirectToFacebook()
    {
        return Socialite::driver('facebook')->redirect();
    }

    public function handleFacebookCallback()
    {
        dd(Socialite::driver('facebook')->user());
    }

after digging in the guzzle files, I was able to get the actual error I'm getting from Facebook which is: OAuth "Facebook Platform" "invalid_code" "This authorization code has been used.", however, I have no idea what this means?

Is there anything obvious I'm missing here?

I also double checked my app config on Facebook, I added the callback url in Settings > Advanced > Valid OAuth redirect URIs which is set to the same url defined on my .env file. My app is set as a Test App and the "parent" app is already set to Live.

Saw a few posts here about similar issues but couldn't find anything definitive.

Thanks for the help!