Add custom post type visible to WP REST API.

I have created a custom post type with the plugin https://wordpress.org/plugins/types/

The post type sigular name is “question”, and it has a custom field group.

add_action( 'init', 'my_question' );
function my_question() {
    $args = array(
            'public'       => true,
            'show_in_rest' => true,
            'label'        => 'questions'
    );
    register_post_type( 'questions', $args );
}

I tried this to get the result when i call the end point /wp-json/wp/v2/questions, but i get empty json array.
I havecreated two question posts and those are published.

Any help please?