EDIT

EDIT1

EDIT2

Here is line 44 to 61 of /abundance/includes/admin/compat.php

function avia_backend_compatibility_custom_field_filter($custom_fields, $post_id)
{
    if(empty($custom_fields))
    {
        $custom_fields['slideshow'][0]['slideshow_image'] = "";
    }

    if(isset($custom_fields['slideshow']) && is_array($custom_fields['slideshow']) && isset($custom_fields['slideshow'][0]['slideshow_image']))
    {
        $post_thumbnail_id = get_post_meta( $post_id, '_thumbnail_id', true );

        if($custom_fields['slideshow'][0]['slideshow_image'] == "" && $post_thumbnail_id)
        {
            $custom_fields['slideshow'][0]['slideshow_image'] = $post_thumbnail_id;
        }
    }
    return $custom_fields;
}

A client's website has 12 pages, but we can both only see 3 of them, even though we have administrator accounts, and creating a new administrator account does not solve the problem.

Screen Options will not open, and if I check the Chrome console, I see:

Failed to load resource: the server responded with a status of 500 (): /wp-admin/edit.php

I can see /wp-admin/edit.php exists.

I have removed /wp-admin and /wp-includes and uploaded fresh copies of these.

I have uploaded a fresh copy of the parent theme, and the child theme is untouched.

If I rename plugins to plugins.temp the issue remains.

Help appreciated.

A client's website has 12 pages, but we can both only see 3 of them, even though we have administrator accounts, and creating a new administrator account does not solve the problem.

Screen Options will not open, and if I check the Chrome console, I see:

Failed to load resource: the server responded with a status of 500 (): /wp-admin/edit.php

I can see /wp-admin/edit.php exists.

I have removed /wp-admin and /wp-includes and uploaded fresh copies of these.

I have uploaded a fresh copy of the parent theme, and the child theme is untouched.

If I rename plugins to plugins.temp the issue remains.

Help appreciated.

EDIT

If I turn debug on, and reload /wp-admin/edit.php?post_type=page, I see the following errors:

Warning: Illegal string offset 'slideshow' in /home/user/public_html/wp-content/themes/abundance/includes/admin/compat.php on line 48

Fatal error: Uncaught Error: Cannot use string offset as an array in /home/user/public_html/wp-content/themes/abundance/includes/admin/compat.php:48 Stack trace: #0 /home/user/public_html/wp-includes/class-wp-hook.php(298): avia_backend_compatibility_custom_field_filter('', 127) #1 /home/user/public_html/wp-includes/plugin.php(203): WP_Hook->apply_filters('', Array) #2 /home/user/public_html/wp-content/themes/abundance/framework/php/function-set-avia-frontend.php(262): apply_filters('avia_post_meta_...', '', 127) #3 /home/user/public_html/wp-includes/class-wp-hook.php(300): avia_post_meta(Object(WP_Post)) #4 /home/user/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters('', Array) #5 /home/user/public_html/wp-includes/plugin.php(515): WP_Hook->do_action(Array) #6 /home/user/public_html/wp-includes/class-wp-query.php(4070): do_action_ref_array('the_post', Array) #7 /home/user/public_html/wp-includes/query.php(938): WP_Query->setup_postdata(Object(WP_Post)) #8 /home/mag in /home/user/public_html/wp-content/themes/abundance/includes/admin/compat.php on line 48