Yii2-bootstrap 4 error not showing

Yii 2.0 General Discussions
1

I’m using the yii2bootstrap4 plugin, and can;t get the error checking to show

in my view i have this

<?php
use yii\helpers\Html;
use yii\bootstrap4\ActiveForm;
use richardfan\widget\JSRegister;
use yii\helpers\Url;

 $form = ActiveForm::begin([
        'id' => $model->formName(),
        'method' => 'post',
        'enableAjaxValidation' => true,
        'validateOnSubmit' => true,
        'enableClientValidation'=> false,
        'options' => ['autocomplete' => 'off'],
    ]);

?>
    <?= $form->field($model, 'email')->textInput(['class' => 'form-control form-control-lg']); ?>
    <?= $form->field($model, 'firstname')->textInput(['class' => 'form-control form-control-lg']); ?>
    <?= $form->field($model, 'lastname')->textInput(['class' => 'form-control form-control-lg']); ?>
    <?= Html::submitButton('Submit', ['class' => 'btn btn-primary btn-block btn-lg shadow-sm']) ?>
    <?php ActiveForm::end(); ?>

<script>
    $(document).ready(function () {  
        var $form = $("#<?= $model->formName() ?>");
        $form.on("submit", function (event, messages) {
            event.preventDefault();
            $.ajax({
                "type":"POST",
                "url":$form.attr('action'),
                "data":$form.serialize(),
                "beforeSend":function( xhr ) {
                },
                "dataType":"json",
                "cache": true, 
                "success":function(data){
                 },                                        
            });
            return false;       
        });
    });
    </script>

in my controller i have this

use yii\bootstrap4\ActiveForm;
use yii\helpers\Json;
use yii\web\Response;

public function actionCheck() {

        //ajax validation
        $model = new User;
        $model->scenario = 'create'; 
        if (Yii::$app->request->isAjax && $model->load(Yii::$app->request->post())) {
            if($model->validate()) {
                $model = User::find()->where('id=:id', [':id' => Yii::$app->user->identity->id])->one();
                $model->firstname = $_POST['User']['firstname'];
                $model->lastname = $_POST['User']['lastname'];
                $model->save();
            } else {
                Yii::$app->response->format = 'json';
                return ActiveForm::validate($model);
            }
            Yii::$app->end();
        }
 return $this->render('check', [
            'model' => new User,
]);
}

the returned JSON if all fields are empty is this


{"user-email":["Email cannot be blank."],"user-firstname":["Firstname cannot be blank."],"user-lastname":["Lastname cannot be blank."]}

any idea what im missing here? Thanks