Why doesn't check for required fields work in yii2?

Question

Yii

Why doesn't check for required fields work in yii2? The model has a rule

public function rules()
    {
        return [
            [['title'], 'required'],

in view form

<?= $form->field($model, 'title')->textInput(['maxlength' => true]) ?>

in the source code, you can see that the field is required

<div class="form-group field-news-title required">
<label class="control-label" for="news-title">Заголовок</label>
<input type="text" id="news-title" class="form-control" name="News[title]" maxlength="255" aria-required="true">

<div class="help-block"></div>
</div>

But nothing works, you leave the title empty and click save, no warning pops up that this field is not filled.
What could be the reason?

Answer 1

Specify that the field cannot be empty.

Answer 2

Look at the console, what's there., maybe js errors. Perhaps the field is not empty, perhaps the validation scripts did not connect at all or do not see the selectors. A million options. It's hard to tell from this description what exactly happened.