In that case, make sure that the address and the port are correct. Did you try to connect with a normal SFTP program (like FileZilla) if the connection is open? And can the SFTP server be reached from your OutSystems server? Where is the OutSystems server located? In the cloud? If so, does the SFTP server allow connections from there?
Anyway, this is very likely an infrastructure problem, not something of the OutSystems Platform or the SFTP component.