This topic has many similar posts, but I'm not finding one that addresses my issue precisely.

Here is what I have done so far:

1. I added a Custom Post Type to functions.php. This works. The imported posts show in the dashboard.

2. I created a custom query to create a category page. This works, I can make it show a few or all of the records, but there are about a hundred posts in this category, so I need pagination.

3. The pagination is producing the correct number of links, and the page addresses are incrementing accordingly.

Here is the code for the template:

<?php
  $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
  $args = array(
    'post_type' => 'lumber',
    'posts_per_page' => 12,
    'paged' => $paged
  );
  $LumberQuery = new WP_Query( $args ); 
?>

<?php 
  if ( $LumberQuery->have_posts() ) : 
    //  echo $LumberQuery -> post_count;
  ?>

    <?php 
      while ( $LumberQuery->have_posts() ) : $LumberQuery->the_post(); 
                echo '<div class="ProductListing">';
                echo '<a href="'.get_permalink().'">';
                the_post_thumbnail( 'thumbnail' );
                echo '</a>';
                the_title( sprintf( '<h2 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h2>' );
                echo '</div><!-- End ProductListing div-->';
      endwhile; 
    ?>

    <div id="Pagination">
    <?php
      $big = 999999999; // need an unlikely integer
 
      echo paginate_links( array(
        'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
        'format' => '?paged=%#%',
        'current' => max( 1, get_query_var('paged') ),
        'total' => $LumberQuery->max_num_pages
       ) );
    ?>
    </div><!-- end pagination -->
    <?php wp_reset_postdata(); ?>

<?php endif; ?>