Custom taxonomy archive is visible to only subscibed users

Question

I have a custom taxonomy (lesson) that helps divide posts and other custom post types between different views over the data. Now I have the custom taxonomy page expanded and visible.

http://www.ascuoladiopencoesione.it/lesson/1-progettare/

You should see an empty page, and that is the issue: Only registered users appear to be able to see the content, and that is strange, because the configuration does not do anything to enforce that...

Thanks

EDIT

This is the structure for the Custom Taxonomy. The custom post type is portfolio_entry, in a theme (enfold)... for other taxonomies and stuff there is no problem, only this doesn't work...

function lessons() {

$labels = array(
    'name'                       => _x( 'Lessons', 'Taxonomy General Name', 'text_domain' ),
    'singular_name'              => _x( 'Lesson', 'Taxonomy Singular Name', 'text_domain' ),
    'menu_name'                  => __( 'Lesson', 'text_domain' ),
    'all_items'                  => __( 'All Lesson Lessons', 'text_domain' ),
    'parent_item'                => __( '', 'text_domain' ),
    'parent_item_colon'          => __( '', 'text_domain' ),
    'new_item_name'              => __( 'New Lesson', 'text_domain' ),
    'add_new_item'               => __( 'Add new Lesson', 'text_domain' ),
    'edit_item'                  => __( 'Edit Lesson', 'text_domain' ),
    'update_item'                => __( 'Update Lesson', 'text_domain' ),
    'separate_items_with_commas' => __( 'Separate Lessons with commas', 'text_domain' ),
    'search_items'               => __( 'Search Lessons', 'text_domain' ),
    'add_or_remove_items'        => __( 'Add or remove Lessons', 'text_domain' ),
    'choose_from_most_used'      => __( 'Choose from the most used Lessons', 'text_domain' ),
    'not_found'                  => __( 'Not Found', 'text_domain' ),
);
$args = array(
    'labels'                     => $labels,
    'hierarchical'               => true,
    'public'                     => true,
    'show_ui'                    => true,
    'show_admin_column'          => true,
    'has_archive'                => true,
    'show_in_nav_menus'          => true,
    'show_tagcloud'              => true
);
register_taxonomy( 'lesson', array( 'post','portfolio','link_category', 'forum', "topic" ), $args );

}

// Hook into the 'init' action
add_action( 'init', 'lessons', 0 );

EDIT added plugins

• bbPress
• Black Studio TinyMCE Widget
• Duplicate Post
• Google Analytics for WordPress
• MailChimp for WordPress Lite
• Page Builder by SiteOrigin
• Responsive Add Ons
• Simple History
• User Role Editor
• User Tags for Wordpress
• Widget Customizer
• WordPress Social Login
• WP Project Manager
• Newsletters Wysija

EDIT - how do I get the posts

$args = array(
    'posts_per_page'   => -1,
    'offset'           => 0,
    'lesson'           => $wp_query->queried_object->name,
    'orderby'          => 'post_date',
    'order'            => 'DESC',
    'post_type'        => array('post', 'portfolio', 'forum', 'link', 'topic', 'link_category'),
    'post_status'      => 'publish',
    'suppress_filters' => true ); 
$myposts = get_posts( $args );
foreach ( $myposts as $post ) : setup_postdata( $post );

Answer 1

I do not in the world know why this works. Yet it does. For future reference...

function remove_meta( $query ) {
    $query->set( 'meta_query', false );
}
add_action( 'pre_get_posts', 'remove_meta' );