Slick Slider is not working in WordPress, Slides not showing

I’m using WordPress. For client testimonials, I have created Custom Post Type which is working fine. After that, I’m creating a shortcode to display post data at the frontend.

Problem – I get all the post data, but I’m not getting a slider.
Output I get – current result

1. I have included slick js and CSS in function.php properly.

function ec_theme_scripts() {
        
        wp_enqueue_style( 'style', get_stylesheet_uri() );
        wp_enqueue_style( 'bootstrap', get_template_directory_uri() . '/css/bootstrap.min.css' );
        wp_enqueue_style( 'custom-css', get_template_directory_uri() . '/css/style.css' );
        wp_enqueue_style( 'slick-css', get_template_directory_uri() . '/css/slick.css' );
        wp_enqueue_style( 'fontawesome-css', 'https://pro.fontawesome.com/releases/v5.15.4/css/all.css' );
        
        
        wp_enqueue_script('bootstrap', get_template_directory_uri() . '/js/bootstrap.min.js', array(), true);
        wp_enqueue_script('jquery', get_template_directory_uri() . '/js/jquery-3.6.0.min.js', array(), true);
        wp_enqueue_script('slick', get_template_directory_uri() . '/js/slick.min.js', array(), true);

    }
    add_action( 'wp_enqueue_scripts', 'ec_theme_scripts' );

2. Here is the WordPress loop code snippet, where I’m fetching slider data from custom post type.

    function create_testimonials_shortcode() {

        $args = array(
            'post_type' => 'Testimonials',
            'publish_status' => 'published',
        );

        register_post_type('Testimonials', $args);

    
        ?>            

            <?php
                $query = new WP_Query($args);
                if( $query -> have_posts() ) :
            ?>        
                        
            <div class="testimonial_slider">

                <?php while( $query -> have_posts() ):
                    $query -> the_post() ;
                ?>
                
                <div class="testimonial-slide">
                    
                    <div class="testimonial-content"> 
                        <p> <?php the_content(); ?> </p>
                    </div>
                    
                    <div class="image-title-wrapper">
                        <?php $img_url = get_the_post_thumbnail_url(get_the_ID(),'full'); ?> 
                        <img src = "<?php echo $img_url; ?>" >
                        <h4 class="testimonial-name"> <?php the_title();?> </h4>
                    </div>

                </div>
                
                <?php endwhile; ?>

            </div>
    
            <?php 
                endif;
                wp_reset_postdata();
            ?>
            
        <?php
    }

    add_shortcode( 'testimonials', 'create_testimonials_shortcode' );

3. At last, Here is the jquery for the slick slider.

$(document).ready(function() {
    $('.testimonial_slider').slick({
        infinite: true,
        slidesToShow: 1,
        slidesToScroll: 1,
        dots: true,
        autoplay: true,
        autoplaySpeed: 5000
    });
});

I have checked everything but didn’t get what has gone wrong exactly.