Connection can not be established. Server name, port number, or credentials may be invalid.
I just got that message when trying to enter a perfectly valid set of connection/credential info into an SSIS package. But testing the connection failed.
Turns out my issue, and maybe your issue too, is that SSIS doesn’t remove white space from the server name textbox. So if you pasted in the name of the FTP server, as I did, you might have fallen victim to the “trailing space” that is frequently copied with your text, and instead of trying to connect to “ftp.com” it tried to connect to “ftp.com ” notice the extra space.