Unable to paginate a custom page query

Question

I have this code on a page called Categories.

<?php
/*
Template Name: Categories
*/

get_header(); ?>

    <section id="primary" class="content-area">

        <main id="main" class="site-main" role="main">

        <header class="page-header">
                <h1 class="page-title">
                    Categories
                </h1>
        </header><!-- .page-header -->

        <?php   

        $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;

        $args = array(
            'post_type' => 'post',
            'posts_per_page' => '4',
            'paged' => get_query_var('paged')
        );
        $the_query = new WP_Query( $args ); ?>

        <?php if ( $the_query->have_posts() ) : ?>

            <?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>

                <?php
                    get_template_part( 'content', 'categories' );
                ?>

            <?php endwhile; ?>

            <?php wp_pagenavi( array( 'query' => $the_query ) ); ?>
            <?php wp_reset_query(); ?>

        <?php endif; ?>

        </main><!-- #main -->
    </section><!-- #primary -->

<?php get_sidebar(); ?>
<?php get_footer(); ?>

I have set the template in admin to page-categories

The pagination shows up with the correct number of pages to browse, however, when I click on the next page (the link is something like example.com/categories/page/2/ ) I get 404 page.

Why is that? how to fix it?

Answer 1

The problem was in the same name for category slug "categories" and the same for the custom page that was holding all categories with the same name "categories".

I have solved that by changing categories slug (in permalinks settings) to singular "category" and I have left custom page as plural "categories".

If somebody know about some better solution, please let me know, thanks.

P.S. I was thinking about deleting this question, however, I think thinks is an interesting problem and maybe somebody will find it helpful. But If any moderator think it's ot worth of sharing, you can delete this question.

Answer 2

This line:

            'paged' => get_query_var('paged')

Should be set to the $paged var you just set, like so:

            'paged' => $paged