Can’t display posts by filtering categories using isotope.js

Can you try:

<?php if (have_posts()): ?>
    <?php while (have_posts()): the_post(); ?>
        <?php
        $categories     = get_the_category();
        $listCategories = [];
        foreach ($categories as $category) {
            $listCategories[] = $category->slug;
        }
        ?>
        <!-- Isotope Grid-Item -->
        <div class="col-md-3 col-sm-4 col-xs-12 isotope-grid-item <?php echo implode(' ', $listCategories); ?>" data-category="<?php echo implode(',', $listCategories); ?>">
            <div class="isotope-item">
                <a href="#">
                    <div class="isotope-feature-image"><?php the_post_thumbnail() ?></div>
                    <h3 class="isotope-title"><a href="<?php the_permalink() ?>"><?php the_title(); ?></a></h3>
                    <p class="isotope-number">Post No: <?php the_ID(); ?></p>
                    <p class="isotope-name">Author: <?php the_author() ?></p>
                    <p class="isotope-type">Blog Type: <?php the_category() ?></p>
                    <p class="isotope-datetime">Post Date: <?php the_date() ?> at <?php the_time() ?></p>
                    <p class="isotope-blog"><?php the_content(); ?></p>
                </a>
            </div>
        </div>
        <!-- Isotope Grid-Item -->
    <?php endwhile; ?>
<?php endif; ?>

Posts can have more than one category, if you look at the source you will probably see [array] or if you put PHP error reporting on you will get an error.