Fatal error: Uncaught TypeError: ftp_nlist(): Argument #1 ($ftp) must be of type FTP\Connection, null given in /home/public/wp-admin/includes/class-wp-filesystem-ftpext.php:438 Stack trace: #0 /home/public/wp-admin/includes/class-wp-filesystem-ftpext.php(438): ftp_nlist(NULL, '/home/public/wp...') #1 /home/public/wp-admin/includes/class-wp-filesystem-ftpext.php(456): WP_Filesystem_FTPext->exists('/home/public/wp...') #2 /home/public/wp-admin/includes/class-wp-filesystem-ftpext.php(757): WP_Filesystem_FTPext->is_file('/home/public/wp...') #3 /home/public/wp-admin/includes/file.php(2772): WP_Filesystem_FTPext->dirlist('/home/public/wp...', false, true) #4 /home/public/wp-content/plugins/wordpress-seo/wp-seo-main.php(361): wp_opcache_invalidate_directory('/home/public/wp...') #5 /home/public/wp-includes/class-wp-hook.php(324): wpseo_init('') #6 /home/public/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array) #7 /home/public/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #8 /home/public/wp-settings.php(506): do_action('plugins_loaded') #9 /home/public/wp-config.php(98): require_once('/home/public/wp...') #10 /home/public/wp-load.php(50): require_once('/home/public/wp...') #11 /home/public/wp-blog-header.php(13): require_once('/home/public/wp...') #12 /home/public/index.php(17): require('/home/public/wp...') #13 {main} thrown in /home/public/wp-admin/includes/class-wp-filesystem-ftpext.php on line 438