Hi there,
It may be a long shot but this could be down to the fact that youre sitting behind a NAT/PAT gateway.
Ftp is one protocol where the source address is baked into the payload of the packet most significantly when using the port command.
So if youre using NAT/PAT then your packet may appear to the FTp server as if its coming from “valid ip address” but when the FTP server looks inside it sees some kind of private address “192.168.1.2” and so the port fails.
A long shot but worth mentioning.
Smiles.
Paula.