The config file /srv/sites/site27/web/config/config.ini.php seems to exist but Matomo could not read it.
» Please check that /srv/sites/site27/web/config/config.ini.php is readable by the user 'site27'.

The Matomo configuration file couldn't be found and you are trying to access a Matomo page.
» You may install Matomo now
If you installed Matomo before and have some tables in your DB, don't worry, you can reuse the same tables and keep your existing data!