Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, first array member is not a valid class name or object in /home/www/professorphd.com/wp-content/plugins/jetpack/class.jetpack-sync.php:47 Stack trace: #0 /home/www/professorphd.com/wp-content/plugins/jetpack/modules/enhanced-distribution.php(12): Jetpack_Sync::sync_posts('/home/www/profe...') #1 /home/www/professorphd.com/wp-content/plugins/jetpack/class.jetpack.php(1142): require('/home/www/profe...') #2 /home/www/professorphd.com/wp-includes/class-wp-hook.php(307): Jetpack::load_modules('') #3 /home/www/professorphd.com/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array) #4 /home/www/professorphd.com/wp-includes/plugin.php(474): WP_Hook->do_action(Array) #5 /home/www/professorphd.com/wp-settings.php(450): do_action('plugins_loaded') #6 /home/www/professorphd.com/wp-config.php(90): require_once('/home/www/profe...') #7 /home/www/professorphd.com/wp-load.php(50): require_once('/home/www/profe...') #8 /home/www/professorphd.com/wp-blog-header.php(13): require_once('/home/www/profe...') #9 /home/www/professorphd.com/index.php(17): require('/home/www/profe...') #10 {main} thrown in /home/www/professorphd.com/wp-content/plugins/jetpack/class.jetpack-sync.php on line 47