Warning: require_once(/var/www/vhosts/tretor.ch/httpdocs/craft/vendor/autoload.php): Failed to open stream: No such file or directory in /var/www/vhosts/tretor.ch/httpdocs/craft/bootstrap.php on line 11

Fatal error: Uncaught Error: Failed opening required '/var/www/vhosts/tretor.ch/httpdocs/craft/vendor/autoload.php' (include_path='.:/usr/share/pear:/usr/share/php') in /var/www/vhosts/tretor.ch/httpdocs/craft/bootstrap.php:11
Stack trace:
#0 /var/www/vhosts/tretor.ch/httpdocs/craft/web/index.php(7): require()
#1 {main}
  thrown in /var/www/vhosts/tretor.ch/httpdocs/craft/bootstrap.php on line 11