Chatwork is always asking user to grant permissions

[tuanpht]

Hello,
I am testing Chatwork Oauth2 with my app. It was successfully granted by user:

However, on next logins, Chatwork still asks user to grant permissions:

Example code:
cw-login.php

<?php
require __DIR__ . '/vendor/autoload.php';

use ChatWork\OAuth2\Client\ChatWorkProvider;

$provider = new ChatWorkProvider(
    getenv('CW_CLIENT_ID'),
    getenv('CW_CLIENT_SECRET'),
    getenv('CW_REDIRECT_URI')
);

$url = $provider->getAuthorizationUrl([
    'scope' => [
        'users.profile.me:read', 
        'rooms.all:read_write',
    ],
]);

echo "<a href='$url'>Login with chatwork</a>";

cw-login-callback.php

<?php
require __DIR__ . '/vendor/autoload.php';

use ChatWork\OAuth2\Client\ChatWorkProvider;
use GuzzleHttp\Client;
use League\OAuth2\Client\Grant\AuthorizationCode;
use League\OAuth2\Client\Grant\RefreshToken;

if (!empty($_GET['error'])) {
    die('User denied your app requests!');
}

if (empty($_GET['code'])) {
    die('Error: no code returned!');
}

$provider = new ChatWorkProvider(
	getenv('CW_CLIENT_ID'),
	getenv('CW_CLIENT_SECRET'),
	getenv('CW_REDIRECT_URI')
);

$accessToken = $provider->getAccessToken((string) new AuthorizationCode(), [
	'code' => $_GET['code'],
]);

echo 'access_token: ' . $accessToken->getToken() . PHP_EOL;

$resourceOwner = $provider->getResourceOwner($accessToken);

echo 'Resource owner: ';
print_r($resourceOwner->toArray());

I think, this issue is not related to this oauth2 client package, but I don't know where to get help.
Please give some advices. Thank you!