“session_start(): open(/var/lib/php/session/sess_s… failed: Permission denied” After enabling Nginx reverse proxy – Plesk 11.5.30 / CentOS 6.5April 21, 2014CentOS 6, Plesk Got the following error right after I enabled Nginx reverse proxy on a Plesk box For us it was as simple as issuing the following to fix this error: chmod 1733 -R session