After a change to the latest version of Filezilla many people are seeing:
Error: GnuTLS error -12: A TLS fatal alert has been received.
Error: Could not connect to server
when using plain ftp as Filezilla have changed the default connection type to “explicit FTP over TLS if available“. If you wish to use FTPs you will need to raise a ticket to get your IP whitelisted.
While we recommend sftp for those wanting to continue using plain ftp you can still revert back to plain ftp if you wish: