Laravel 5.3 Passport is not working

Question

I am new in Laravel Passport and installed and configured with official documentation.

public function register(){
    $password = Hash::make('demo');
    $user = DB::table('users')->insertGetId([
          'name'     => 'User',
          'email'    => '[e-mail]',
          'password' => $password,
        ]);

     // create oauth client
    $oauth_client = \App\OauthClient::create([
        'user_id'                => $user,
        'name'                   => 'User',
        'secret'                 => base64_encode(hash_hmac('sha256',$password, 'secret', true)),
        'password_client'        => 1,
        'personal_access_client' => 0,
        'redirect'               => '',
        'revoked'                => 0,
    ]);

    $response = ['status'=>200,'message'=>'Successfully Registered'];
    return $response;

I just run the API throgh postman and its getting response as Successfully Registered

After that I just called the http://localhost/passport/oauth/token route to authenticate the user. But its not working. Its returning like..

Postdata :

grant_type:password
client_id :1
client_secret:j7q0ky8chHQ0RHJFpWo4Lqn/hl7Z0ntzYeyzsXE9ULA=
username:[e-mail]
password:demo
scope:

Response :

{
   "error": "invalid_request",
   "message": "The request is missing a required parameter, includes an invalid parameter value, includes a parameter more than once, or is otherwise malformed.",
   "hint": "Check the `client_id` parameter"
} 

Answer 1

Make sure it is placed in body not in params.

Answer 2

Still not sure why, but running php artisan config:clear fixed this for me.