Warning: require_once(/volume1/web/phpbb/vendor/composer/autoload_real.php): Failed to open stream: No such file or directory in /volume1/web/phpbb/vendor/autoload.php on line 5

Fatal error: Uncaught Error: Failed opening required '/volume1/web/phpbb/vendor/composer/autoload_real.php' (include_path='.:/usr/share/pear') in /volume1/web/phpbb/vendor/autoload.php:5
Stack trace:
#0 /volume1/web/phpbb/includes/startup.php(83): require()
#1 /volume1/web/phpbb/common.php(23): require('/volume1/web/ph...')
#2 /volume1/web/phpbb/viewforum.php(20): include('/volume1/web/ph...')
#3 {main}
  thrown in /volume1/web/phpbb/vendor/autoload.php on line 5