500 Internal server error
PHP version is set to 7.x in Domains > example.com > PHP Settings
The following error is seen in
WARNING: [pool example.com] child 1159 said into stderr: "NOTICE: PHP message: PHP Fatal error: The file /var/www/vhosts/example.com/app/helpers/facebook_helper.php was encoded by the ionCube Encoder for PHP 5.x and cannot run under PHP 7.x or later."
Domain was built for the PHP version 5.x and does not work properly with PHP version 7.x.
Review the domain's code to update it to the 7.x version or change the PHP version for this domain to an appropriate version:
Go to Domains > example.com > PHP Settings and change version to the 5.x.
Note: Additional custom PHP handlers could be installed following the next article if needed.