II’ve created a post type to add campaigns to my site. And I’m trying to get all the posts and display them on an archive.php page and also a single.php page to display the individual campaigns.
But when I display them on the site I get 404 errors: page not found.

I try to create two files to display alls campaigns:

This is my custom-post-type.php file

<?php
// Register a custom post type for campaigns
function fp_create_campaign_post_type() {
    register_post_type('campaign',
        array(
            'labels' => array(
                'name' => __('Campagnes'),
                'singular_name' => __('Campagne'),
                'add_new' => __('Ajouter une campagne'),
                'add_new_item' => __('Ajouter une campagne'),
                'edit_item' => __('Modifier la campagne'),
                'new_item' => __('Nouvelle campagne'),
                'view_item' => __('Voir la campagne'),
                'search_items' => __('Rechercher parmi les campagnes'),
                'not_found' => __('Aucune campagne trouvée'),
                'not_found_in_trash' => __('Aucune campagne trouvée dans la corbeille')
            ),
            'public' => true,
            'has_archive' => "campaign",
            'supports' => array('title', 'editor', 'thumbnail')
        )
    );
}
function custom_post_type_list_shortcode() {
    ob_start();

    $type = 'custom_post_type';
    $args = array(
        'post_type' => $type,
        'post_status' => 'publish',
        'posts_per_page' => -1,
        'ignore_sticky_posts' => true
    );
    $my_query = new WP_Query($args);

    if ($my_query->have_posts()) :
        echo '<ul>';
        while ($my_query->have_posts()) : $my_query->the_post();
            echo '<li><a href="' . get_permalink() . '">' . get_the_title() . '</a></li>';
        endwhile;
        echo '</ul>';
    else :
        echo '<p>Aucune publication trouvée.</p>';
    endif;

    wp_reset_postdata();

    return ob_get_clean();
}
add_shortcode('custom_post_type_list', 'custom_post_type_list_shortcode');


add_action('init', 'fp_create_campaign_post_type');

This is my template-campaign.php file, it must display alls projects

<?php
/*
Template Name: Campagnes de financement participatif
*/

get_header();

//personnalisée pour afficher les articles de type "campaign"
$args = array(
    'post_type' => 'campaign',
    'posts_per_page' => -1, // Afficher tous les articles
);

$query = new WP_Query($args);

if ($query->have_posts()) :
    while ($query->have_posts()) :
        $query->the_post();

        // Affichage du titre de l'article
        echo '<h2>' . get_the_title() . '</h2>';

        // Affichage de la barre de progression
        echo fp_get_campaign_progress_bar(get_the_ID());

    endwhile;
    wp_reset_postdata();
else :
    echo 'Aucune campagne trouvée';

endif;

get_footer();
?>