I have seen this when the SFTP service is not running on the backup server or when you have configured the SFTP server to only accept connections from specific IP addresses. Also be sure that you are using SFTP, not an FTPS server. This is not FTP!
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.