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/httpd/vhosts/gastrorent.ch/httpdocs/wp-content/plugins/jetpack/class.jetpack-sync.php:47
Stack trace:
#0 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-content/plugins/jetpack/modules/enhanced-distribution.php(12): Jetpack_Sync::sync_posts('/home/httpd/vho...')
#1 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-content/plugins/jetpack/class.jetpack.php(1142): require('/home/httpd/vho...')
#2 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-includes/plugin.php(496): Jetpack::load_modules('')
#3 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-settings.php(237): do_action('plugins_loaded')
#4 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-config.php(79): require_once('/home/httpd/vho...')
#5 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-load.php(37): require_once('/home/httpd/vho...')
#6 /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-blog-header.php(12): require_once('/home/httpd/vho...')
#7 /home/httpd/vhosts/gastrorent.ch/httpdocs/index.php(17): require('/home/httpd/vho...')
#8 {main}
  thrown in /home/httpd/vhosts/gastrorent.ch/httpdocs/wp-content/plugins/jetpack/class.jetpack-sync.php on line 47