admin-ajax php not working in new WordPress versio

Question

I have a website that was in version 4.7.6 and made an update to 4.8.3 which is the current one. After the update, I noticed that the ajax call is not working. When I inspected the page and went to network, I see the long green bar about the admin-ajax.php as you can see in the image.

The php file code that is being read for that particular page looks like this:

<?php
/**
* The template used for displaying List of tours of category
*
* @package WordPress
* @subpackage Twenty_Sixteen
* @since Twenty Sixteen 1.0
*/
?>
<?php

$limit = get_field('tour_per_page', 'option');

$queried_object = get_queried_object();

$title_color = '';
if ($queried_object->taxonomy):
    $taxonomy = $queried_object->taxonomy;
    $cat_title = $queried_object->name;
    $term_id = $queried_object->term_id;

    $parents = get_category_parents($term_id);
    $parent = explode('/', $parents);
    $parent_term = get_term_by('slug', $parent[0], 'tour_category');

    $color = get_field('category_color', $taxonomy . '_' . $parent_term->term_id);
//    $color = get_field('category_color', $taxonomy . '_' . $term_id);
    $banner = get_field('category_banner', $taxonomy . '_' . $parent_term->term_id);
    $cat_image = get_field('category_image', $taxonomy . '_' . $term_id);

    $rgba1 = hex2rgba($color, 1);
    $rgba2 = hex2rgba($color, 0.7);

    $title_color = ($rgba2) ? 'background:' . $rgba2 . ';' : '';
endif;
$style = '';
if ($banner):
    $style = "background:url('" . $banner . "'); background-position: 50% 50% ; background-size: cover;";
endif;
?>
<!-- top banner -->
<div class="inner-banner-wrap africa-banner" style="<?php echo $style; ?>">
    <div class="container">
        <div class="row">
            <div class="col-xs-12">
                <div class="inner-banner-text">
                    <?php if ($cat_title): ?>
                        <div class="banner-title" style="<?php echo $title_color; ?>">
                            <?php if ($cat_image): ?>
                                <span><img src="<?php echo $cat_image; ?>" alt="africa-map"></span>
                                <?php
                            endif;
                            echo $cat_title;
                            ?>
                        </div>
                    <?php endif; ?>
                </div>
            </div>
        </div>
    </div>
</div>
<!-- end top banner -->

<!-- Bread Crumb Menu Start-->
<div class="container">
    <?php get_template_part('template-parts/content', 'breadcrumb'); ?>


</div>
<!-- Bread Crumb Menu End-->


<div class="travel-event-wrap blog-wrap travel-listing-wrap">

    <div class="container">
        <div class="row">
            <!-- Start Sidebar-->
            <div class="col-xs-12 col-md-3">
                <div class="filter-list-section" id="filter-list-section"><ul></ul></div>
                <div class="side-bar-wrap">
                    <?php dynamic_sidebar('search_tour'); ?>
                </div>
            </div>
            <!-- End Sidebar -->
            <?php
            // only run this on category pages
            $this_cat = &get_category($wp_query->get_queried_object_id());
            $count = $this_cat->count;
            ?>
            <!-- Tour List Section Start-->
            <div class="col-xs-12 col-md-9">
                <div class="desc-block">
                    <h1 style="color:<?php echo $rgba1; ?>"><?php echo $this_cat->name; ?></h1>
                    <p><?php echo category_description($this_cat->term_id); ?></p>
                </div>

                <div class="filter-bar clearfix">
                    <div class="event-number pull-left">
                        <span></span> rundresor tillgängliga
                    </div>
                    <?php dynamic_sidebar('sort_tour'); ?>
                </div>


                <div id="event-list-wrap" class="event-list-wrap"></div>
                <!-- Tour List Section End-->

                <input type="hidden" id="limitstart" value="0"/>
                <input type="hidden" id="limit" value="<?php echo $limit; ?>"/>
                <input type="hidden" id="totaltour" value="<?php echo $count; ?>"/>
                <div id="loadmore" class="text-center" style="display: none;"><img
                        src="<?php echo get_template_directory_uri() . "/images/loading.gif"; ?>"></div>
            </div>
        </div>
    </div>
</div>
<script>
    var xhr;
    jQuery(document).ready(function () {
        jQuery('#loadmore').show();
        loaddata();
        if (navigator.userAgent.indexOf('MSIE') !== -1 || navigator.appVersion.indexOf('Trident/') > 0) {
            jQuery('body').scroll(function () {            
               if( (jQuery('body').scrollTop() + jQuery('body').height()) >= ( jQuery(document).height()    - jQuery("#footer_div").height()  ) )
               {
                    var limitstart = jQuery('#limitstart').val();
                    var totaltour = jQuery('#totaltour').val();
                    if (parseInt(limitstart) < parseInt(totaltour)) {
                        jQuery('#loadmore').show();
                        loaddata();
                    } else {
                        jQuery('#loadmore').hide();
                    }
                }
            });
        }else{
            jQuery(window).scroll(function () {
               if( (jQuery(window).scrollTop() + jQuery(window).height()) >= ( jQuery(document).height()    - jQuery("#footer_div").height()  ) )
               {
                    var limitstart = jQuery('#limitstart').val();
                    var totaltour = jQuery('#totaltour').val();
                    if (parseInt(limitstart) < parseInt(totaltour)) {
                        jQuery('#loadmore').show();
                        loaddata();
                    } else {
                        jQuery('#loadmore').hide();
                    }
                }
            });
        }
    });

    function loaddata() {
        var formSort = jQuery('#sortTour').serialize();
        var formSearch = jQuery('#searchTour').serialize();
        var ajaxurl = '<?php echo admin_url('admin-ajax.php'); ?>';
        var limitstart = jQuery('#limitstart').val();
        var limit = jQuery('#limit').val();
        var data = {
            'action': 'filter_tour',
            'formSort': formSort,
            'formSearch': formSearch,
            'limitstart': limitstart
        };
        if (xhr && xhr.readyState != 4 && xhr.readyState != 0) {
            xhr.abort();
        }
        xhr = jQuery.post(ajaxurl, data, function (response) {
            jQuery('.bakdrop').hide();
            jQuery('.loader').hide();
            var data = JSON.parse(response);
            jQuery('#event-list-wrap').append(data.html);
            jQuery('#totaltour').val(data.total_tour);
            jQuery('.event-number span').html(data.total_tour);
            limitstart = parseInt(limitstart) + parseInt(limit);
            jQuery('#limitstart').val(limitstart);
            jQuery('#loadmore').hide();
        });
    }
</script>

I initially thought it is because the javascript code is not in a separate js file and enqueued so I had done that but made no difference.

Is there anything with the ajax call? Hope you can help.