Code Injection to add Pagination menu not working

I had this code on my Portfolio page and it was fine until this weekend (below)

It is now removing all background colours from the main portfolio page and the interior portfolio pages. 

The goal of the code is to create a menu bar of pagination at the bottom of the interior portfolio pages in lieu of the pagination. I think I saw this on the forum by @tuanphan but can't find it now.

Any idea what is causing the error?  Below is what it looks like now with the code (top) and what its supposed to look like (middle). The bottom image shows the pagination i'm talking about.
 

Currently, I've removed the code but we are about to go live and will have to add back Squarespace pagination if I can't get this figured out.

 

Thank you!

 

website: https://done-right-decks.squarespace.com/gallery

password: doneright

 

 

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>;
  <script>
$(document).ready(function() { 
        $('<section class="item-pagination item-pagination--prev-next under-pagination"><div class="sqs-block html-block sqs-block-html"><div class="sqs-block-content"><p><a href="/gallery" target="_blank">MAIN GALLERY</a> | <a href="/gallery/decks">DECKS</a> | <a href="/gallery/outdoor-living">OUTDOOR LIVING</a> | <a href="/gallery/fencing">FENCING</a> | <a href="/gallery/interior-renovations">INTERIOR RENOVATIONS</a></p></div></div></section>').insertAfter('.item-pagination[data-collection-type^="portfolio"]');
    });
    </script>
    <style>
    section.under-pagination {
    justify-content: center;
    padding-top: 10px;
    padding-bottom: 10px;
 
}