Backup to FTP fails in active mode if Plesk firewall uses default settings: unable to list directory: Curl error: (28) Timeout was reached

Symptoms

Backup to FTP fails in active mode if Plesk firewall uses default settings:

PLESK_ERROR: Error: Unable to access to the storage:
Transport error: unable to list directory: Curl error: (28) Timeout was reached: Last FTP request: LIST -a Last FTP response: 200 Type set to A Make sure you have entered the correct storage settings.
You can check them independently with the command: curl -v -P - -u ftpuser ftp://203.0.113.2

"Use passive mode" option in Backup Manager > FTP Storage Settings is disabled

Cause

This is an internal issue with ID #PPPM-6170 , which is planned to be fixed in future product updates.

Resolution

As a workaround, use passive mode for FTP connection: Tools and Settings > Backup Manager > FTP Storage Settings