SFTP Send File - 'Connection refused' Error

Hello,

SFTP Send File smart service is failing with the error Connection refused. Third-party credentials are setup and have not changed. The plugin has access to the third party credentials.

We are passing the values to the smart service as below:

            File Transfer Configurations: 'type!{plugins.ps.appiancorp.com/.../}FT_Config'(

            serverHostName: cons!SFTP_HOST_NAME, (text)

            serverPort: cons!SFTP_SERVER_PORT_NUMBER, (integer)

            scsExternalSystemKey: cons!SFTP_EXTERNAL_SYSTEM_KEY, (text)

            usePerUserCredentials: false(), (boolean)

           )

           Remote File Path: /filePath/fileName.pdf

           Document To Send: Document

Can you please let me know what is causing the error? Thank you in advance!