captcha not working using scenarios in yii2 - yii2

Question

I am trying to add captcha validation based on scenario, for which I am first retrieving number of failed attempts from database. For which I am using checkattempts() function. Based on the result I am displaying captcha in view and adding scenario condition in controller as below.
In LoginForm model:
public function rules()
{
return [
[['username', 'password'], 'required', 'on'=>'loginpage'],
[['username', 'password'], 'required', 'on'=>'withCaptcha'],
[['reference_url'], 'safe'],
[['verifyCode'], 'captcha', 'skipOnEmpty' => true,'on'=>'withCaptcha'],
['username','email', 'on'=>'loginpage', 'message'=> 'Please enter a valid email address'],
['password', 'validatePassword', 'on'=>'loginpage'],
['password', 'validatePassword', 'on'=>'withCaptcha'],
];
}
public function checkattempts($uname)
{
$user = \frontend\models\User::findByEmail($uname);
$ip = $this->get_client_ip();
if($user){
$data = (new Query())->select('*')
->from('login_attempts')
->where(['ip' => $ip])->andWhere(['user_ref_id' => $user->id])
->one();
if($data["attempts"] >=3){
return true;
}else{
return false;
}
}
return false;
}
in SiteController.php controller
public function actionLogin() {
if (!\Yii::$app->user->isGuest) {
return $this->redirect(Yii::$app->getUrlManager()->getBaseUrl() . '/../../');
}
$model = new \common\models\LoginForm();
$model->scenario = 'loginpage';
$captcha = false;
if(Yii::$app->request->post()){
$post_variables =Yii::$app->request->post('LoginForm');
if ($model->checkattempts($post_variables['username'])) {
$model->scenario = 'withCaptcha';
$captcha = true;
}
}
if ($model->load(Yii::$app->request->post()) && $model->validate()) {
$model->login(); print_r($model->getErrors()); exit;
} else {
return $this->render('login', [
'model' => $model, 'captcha' => $captcha,
]);
}
In my login.php view:
<?php if($captcha) { ?>
<?= $form->field($model, 'verifyCode')->widget(Captcha::className(),
['template' => '<div class="captcha_img">{image}</div>'
. '<a class="refreshcaptcha" href="#">'
. Html::img('/images/imageName.png',[]).'</a>'
. 'Verification Code{input}',
])->label(FALSE); ?>
<?php } ?>
In my controller when I am tring to print model errors at $model->login() function it is giving below error everytime even though the verification code is correct.
Array ( [verifycode] => Array ( [0] => The verification code is incorrect. ) )
Why is it failing every time. Is there any mistake in the code written?
Thanks in advance