Wordpress custom wp_query archive page 2 not found

Question

I have a custom WP_Query to for archive.php. I have fixed the pagination issue I was having by following this great answer here . And I'm using this answer from here to help me find the category without having to define each category.

I need to use wp_query as I'm changing layouts and inserting different content after X amounts of posts. However I have removed all of this whilst testing the pagination.

When I use the pagination to go to /page/2/ it says 'Page not found'. I thought this would be a simple permalink update. I've gone into my permalink settings multiple times and re-saved them but it hasn't fixed the page not found issue.

Below is my code. I'm not sure if there is something in this thats causing the issue.

<?php
global $query_string;

$query_args = explode("&", $query_string);

// Define custom query parameters
$archive_query = array(
    'posts_per_page'=> 3
);

// Get current page and append to custom query parameters array
$archive_query['paged'] = get_query_var( 'paged' ) ? get_query_var( 'paged' ) : 1;

foreach($query_args as $key => $string) {
    $query_split = explode("=", $string);
    $archive_query[$query_split[0]] = urldecode($query_split[1]);
} // foreach


// Instantiate custom query
$query = new WP_Query($archive_query);

// Pagination fix
$temp_query = $wp_query;
$wp_query   = NULL;
$wp_query   = $query;



    // Output custom query loop
if ( $query->have_posts() ) :
    while ( $query->have_posts() ) : $query->the_post();?>

        <h1><?php the_title();?></h1>    

    <?php endwhile;
endif;
wp_reset_postdata();

?>

<div id="pagination-wrapper">
    <?php 
        previous_posts_link( 'Older Posts' , $query->max_num_pages  );
        next_posts_link( 'Newer Posts', $query->max_num_pages ); 
    ?>

</div>
<?php
// Reset main query object
$wp_query = NULL;
$wp_query = $temp_query; 
?>

Answer 1

If you aren't using the main loop I think it would be easier changing it rather then creating a new query and dealing with it.

You could add

function alter_category_posts_per_page( $query ) {
    if ( $query->is_category() && $query->is_main_query() ) {
        $query->set( 'posts_per_page', '3' );
    }
}
add_action( 'pre_get_posts', 'alter_category_posts_per_page' );

to your theme functions.php to achieve that.

If it doesn't work at all you probably have some content using the same slug as the category.