Exactly what I've done and always done but it's not connecting. I've been putting either 21 in port or leaving it blank but it's still the same.Put the box ip address in HOST
Put root in USERNAME
Put password in PASSWORD
Click quick connect
Edit: Panic over. Just found this on another thread - ' With ATV 6.4 a password needs to be set, Menu -> Setup -> System -> Network -> Password setup '
Now able to log into Filezilla. Phew!