Unable to add backup service node. The Task "Install additional packages on node according role
PPA_BACKUP failed with the following error:
Unable to execute the command '/usr/local/psa/bin/server_pref'. Unable to make test connection with to specified. Please check login, password and FTP mode (-use-ftp-passive-mode option). Details: Unable to connect to FTP server: pmm-ras error (Error code = 1): Repository error: Transport error: unable to list directory: Curl error: FTP: couldn't retrieve (RETR failed) the specifie
Connectivity issue with FTP server.
Check whether the firewall does not restrict the connections to through 21 port. By default Passive ports for is not defined for the FTP (proftpd) installed by Plesk Automation (PA). In case you set up the passive ports manually, make sure they are opened too.
For additional information check following article.