ResolutionIf you see an empty page in the Parallels Plesk Panel (PP) Control Panel (CP) instead of the page you are trying to access, it means that an error has occurred. By default, PP does not show PHP errors for security reasons.
To enable PHP error reporting, you can edit $PRODUCT_ROOT_D/admin/conf/php.ini and set:
display_errors = On
Restart the PP CP after that. You should now be able to see the exact error and fix it.
Also, see this article: "Failed opening 'auth.php3' for inclusion" PHP error."