Ftp is a not trivial protocol.

First, it relies on 2 network connections. One is the "Command and Control" channel (login, change directory, download command, upload command, change data channel configuration,..), the other one is the "Data" channel where the transfer really happen (download, upload, ls: list files)
Secondly, you can configure the data channel in two way: Passive FTP and Active FTP.

If you cannot login it means that the Command and Control TCP port (21 by design) is not reachable: Either the ftp server is not started or the firewall/NAT is not letting through the connection to port 21.
If you can login but cannot issue a ls/download/upload then your data channel is getting blocked.

Passive, active ftp, a definitive guide


In the menu, you can try to change it from active to passive or vice-versa. I'll try it a bit more to see if everything works.
All tests should be made without firewall and preferably locally first (no Router in between).