Converting Authorization Codes To Access Tokens

The keys used to encrypt and decrypt when exchanging the authorization code to an access token are different. Why, how come? Can anyone give a hand?

:: I've followed the instructions here : https://laravel.com/docs/5.6/passport#installation To install multiple times a laravel project with Passport as an openauth server, And also multiple tries of client installations to test connectivity. Doing this on my localhost Win10 machine, Apache 2.4, Mysql . Have setup multiple virtual hosts for the server ,and the client respectively, running on different ports.

I was never able to fully get it running, it always fails at the authorization code exchange to an access token, and at the bottom of it is what i think are different keys used for encryption of the authorization code and decryption when received back from the client.

More precisely, i have the following code in my client:

Route::get('/callback', function (Request $request) {

/* return '

    
    
    
    
    
    
';
*/
$http = new GuzzleHttp\Client;

$fp = fopen('guzzle.log.txt','a');
$response = $http->post('http://passport:8090/oauth/token', [
'exceptions' => false,
'debug' => $fp,
'form_params' => [
'grant_type' => 'authorization_code',
'client_id' => '3',
'client_secret' => 'jOf6XcL4yv5WqSAmKwgKaKab6Drx5OJnMcMwp3rw',
'redirect_uri' => 'http://client:8091/callback',
'code' => $request->code,
],
]);
print_R((string)$response->getBody());
fclose($fp);
exit;
return json_decode((string) $response->getBody(), true);

});
I keep getting the following error:
local.ERROR: The request is missing a required parameter, includes an invalid parameter value, includes a parameter more than once, or is otherwise malformed. {"exception":"[object] (League\OAuth2\Server\Exception\OAuthServerException(code: 3): The request is missing a required parameter, includes an invalid parameter value, includes a parameter more than once, or is otherwise malformed. at \work\laravel\passport\vendor\league\oauth2-server\src\Exception\OAuthServerException.php:114
Very interesting is that if instead of the guzzleHttp curl call, i manually submit the form (commented out in the code above), that successfully returns a 200 with bearer token a.s.o.
Does anyone have any idea why or any hints to fix?