there could be several root causes, why you should consider to post at least the necessary informations for further investigations:
Output of the command:
Code:
plesk version
Pls. post your corresponding entries from "/var/log/messages" ( for CentOS/RHEL - based systems ), or "var/log/syslog" ( on Debian/Ubuntu - based systems ).
Pls. post your corresponding entries from "/var/log/psa-horde/psa-horde.log".
Pls. check possible corresponding entries from your webserver "error_log".
Pls. check possible corresponding entries from "/var/log/audit/audit.log"
Do you use SELinux on your server? Did you check that there are no misconfigurations, IF YOU USE SELinux?