Symptoms

• Passive FTP connection does not work after enabling Plesk Firewall Tools & Settings > Firewall > Enable .
• Cannot list directory when connecting in passive mode:
  

  ftp> dir
  227 Entering Passive Mode (192,0,2,2,176,121).
  ftp: connect: Connection timed out

• ip_conntrack_ftp module is not loaded:
  

  # lsmod | grep conntrack_ftp
  #

Cause

The described behavior is expected if ip_conntrack_ftp module is not loaded.

This is Plesk bug with ID # PPPM-6187. The notification in Plesk UI will be added in future Plesk updates.

Resolution

As a workaround, configure passive ports as described in the article How to configure a passive ports range for ProFTPd on a server behind a firewall .