Passive Ports

Chances are your Passive Ports are not set in your PLESK ProFTPD configuration.

To fix that edit:

vim /etc/proftpd.d/50-plesk.conf

Add a PassivePorts range to allow simultaneous FPT connections.

Your configuration should be like this:

#ATTENTION!
#
#DO NOT MODIFY THIS FILE BECAUSE IT WAS GENERATED AUTOMATICALLY,
#SO ALL YOUR CHANGES WILL BE LOST THE NEXT TIME THE FILE IS GENERATED.

# Global section
<Global>
<IfModule mod_tls.c>
    TLSEngine on
    TLSRequired off
</IfModule>
</Global>
# Global section
<VirtualHost 172.26.12.243>
MasqueradeAddress 13.230.187.48
PassivePorts 30000 30400
</VirtualHost>

Restart ProFTPD with the following command (PLESK use xinetd for this):

sudo service xinetd restart

Try to reconnect via FTP.

Firewall configuration

If you have PLESK Firewall enabled, add the passive ports range to your rules.

PLESK Firewall rules can be added via the PLESK dashboard in: Tools & Settings > Firewall

Once your rules have been reloaded, try again to connect to the FTP.

Top Level Firewall

If it’s still not working, verify that no other firewalls are running at a higher level (managed by your hosting provider).

Hope this article will help :) Feel free to leave a comment below for any improvement.