sFTP issue

The problem:

A vendor wants data sent either via FTP/SSL or sFTP. Can't make a connection
using either method.

HOWEVER, on a pc running FileZilla, the transfer works.

The contact I have tells me that everybody uses FileZilla. Really? He knows
little about sftp - his words.

I do not understand why FileZilla works and sFTP won't. All I get is that a
connection could not be made.

One other bit that probably makes the difference is that he site requires both
key pair and username/password.

Ne has no idea how to get key pair working. I am wondering if that is why sFTP
times out.

How would I be able to tell on myy end why FTP/SSL or sFTP do not connect?

Thanks.

John McKee