Why is there an error in Postman response when authorizing using YII2 token?

Question

API

Good afternoon! Given the API on YII2, you will need to implement the frontend, but when you try to get responses in Posman, an error is displayed. For example, when logging in. Set {'login':'user15335551863','password':'pass'} and the corresponding url. The error is displayed:

In the User model:

public function login()
    {
        if($this->validate()) {

            $user = self::findOne(['login' => $this->login]);

            $user->token = Yii::$app->security->generateRandomString();
            $user->save();

            return [
                'token' => $user->token
            ];
        } else {
            return [
                'errors' => $this->errors
            ];
        }

In controller:

public function actionLogin()
    {
        $user = new User();
        $user->load(Yii::$app->request->post(),'');
        $user->scenario = 'login';
        return $user->login();
    }

In web.php:

'urlManager' => [
            'enablePrettyUrl' => true,
            'showScriptName' => false,
            'rules' => [
                'POST /api/login' => 'user/login',
                [
                    'class' => 'yii\rest\UrlRule',
                    'controller' => ['user'],
                ],

API deployed on OpenServer. Run a composer update. We created a database and registered it in db.php. Then they began to test in Postman and an error appears.
Tell me, what could be the reason for such an error?