The error message "Unable to save remote backup FTP server settings: Error: Unable to access to the storage: Transport error: unable to list directory: Curl error: (9) No such file or directory" in Plesk suggests that there might be an issue with the directory path specified for the remote FTP server.

To address this issue, you can try the following steps:

1. Verify FTP Server and Path:

   • Double-check the FTP server address and directory path you've entered in the remote backup settings. Make sure they are accurate and point to a valid directory on the FTP server.

2. Check FTP Credentials:

   • Ensure that the FTP username and password you've provided have the necessary permissions to access the specified directory on the remote server.

3. Test FTP Connection with a Client:

   • Use an FTP client (such as FileZilla) to connect to the remote server using the same credentials and directory path. This will help verify if there are any issues with the FTP server itself.

4. Ensure Directory Exists:

   • Make sure that the directory specified for backups on the remote FTP server actually exists. If it doesn't, create it manually.

5. Check Firewall and Network Restrictions:

   • Verify that there are no firewall rules or network restrictions blocking the connection to the remote FTP server. Ensure that the necessary ports (usually 21 for FTP) are open.

6. Use Passive FTP Mode:

   • Try enabling passive mode for the FTP connection in the Plesk backup settings. Passive mode may help in cases where there are firewall issues.

7. Test with Another FTP Client:

   • If possible, try connecting to the remote FTP server using a different FTP client (outside of Plesk). This can help isolate whether the issue is specific to Plesk or if it's related to the FTP server configuration.

8. Check FTP Server Logs:

   • Review the logs on the remote FTP server for any error messages or warnings that might provide more context about the issue.

9. Contact FTP Server Provider:

   • If the FTP server is managed by a third-party provider, consider reaching out to them for assistance in verifying the settings and troubleshooting any issues on their end.

10. Contact Plesk Support:

    • If none of the above steps resolve the issue, consider reaching out to Plesk support for further assistance. They can provide specific guidance based on your server's configuration.

By following these steps, you should be able to address the issue and successfully save the remote backup FTP server settings in Plesk. Remember to always back up your data before making significant changes to ensure you can revert to a stable state if needed.