Question

I recently migrated a WordPress network of two sites from a local MAMP server to an online one. Everything migrated perfectly, except the functionality of the Post-Thumbnail. The meta box is simply not appearing in any site, in any theme across the network.

I’ve tested a few different themes with post-thumbnail enabled, and the result is the same. No metabox is visible! I’m rather stumped, does anyone have suggestions?

The functions.php file for one of the sites is:

if(function_exists('add_theme_support')) {
    add_theme_support('post-thumbnails', array( 'page', 'post', 'portfolio' ));

    /** Register custom size */
    add_image_size('page-image', 620, 620, false);
    add_image_size('portfolio-image', 795, 575, true);
    add_image_size('portfolio-thumbnail', 135, 94, true);
}



//------enable post thumbnail preview for custom columns 
if ( !function_exists('fb_AddThumbColumn') && function_exists('add_theme_support') ) {

    // for post and investments

    function fb_AddThumbColumn($cols) { 
        $cols['thumbnail'] = __('Thumbnail'); 
        return $cols;
    }

    function fb_AddThumbValue($column_name, $post_id) {

            $width = (int) 200;
            $height = (int) 125;


            if ( 'thumbnail' == $column_name ) {
                // thumbnail of WP 2.9
                $thumbnail_id = get_post_meta( $post_id, '_thumbnail_id', true );
                // image from gallery
                $attachments = get_children( array('post_parent' => $post_id, 'post_type' => 'attachment', 'post_mime_type' => 'image') );
                if ($thumbnail_id)
                    $thumb = wp_get_attachment_image( $thumbnail_id, array($width, $height), true );
                elseif ($attachments) {
                    foreach ( $attachments as $attachment_id => $attachment ) {
                        $thumb = wp_get_attachment_image( $attachment_id, array($width, $height), true );
                    }
                }
                    if ( isset($thumb) && $thumb ) {
                        echo $thumb;
                    } else {
                        echo __('None');
                    }
            }
    }

    // for posts
    add_filter( 'manage_posts_columns', 'fb_AddThumbColumn' );
    add_action( 'manage_posts_custom_column', 'fb_AddThumbValue', 10, 2 );

    // for portfolio
    add_filter( 'manage_portfolio_columns', 'fb_AddThumbColumn' );
    add_action( 'manage_portfolio_custom_column', 'fb_AddThumbValue', 10, 2 );
}
*/

function the_post_thumbnail_url($post_id) {
  echo wp_get_attachment_url( get_post_thumbnail_id($post_id) );
}

Answer 1

You must switch to Network Admin mode

then go to

Settings > Network settings

near the end you’ll find

Upload Settings > Media upload buttons

I checked Images to see the Featured Image box appears in my New Post admin page.