Plesk home page shows a blank page or
500 Internal Server Error .
The log file
/usr/local/psa/admin/logs/panel.log contains the following output:
03-Jul-2014 16:28:26 Europe/Berlin] PHP Fatal error: require_once(): Failed opening required 'modules/firewall/FwConfigurator.php' (include_path='/usr/local/sb/include:/opt/psa/admin/plib:/opt/psa/admin/externals:/usr/local/sb/include:/usr/local/sb/include/PEAR') in /opt/psa/admin/application/admin/controllers/HomeController.php on line 104
`FwConfigurator.php` is a part of Plesk firewall module, but this was not properly installed.
A corrupted Plesk Firewall extension.
Install the extension using the following command:
# /usr/local/psa/admin/bin/autoinstaller --select-release-current --install-component psa-firewall