Why ExistingLister invalid in the FTP tab

Go C:\ ExistingLister work fine
when I want to go a ftp tab, I change C:\ to a ftp tab label(Go ftp://xxx.xxx.xxx.xxx/httpdocs ExistingLister)
it can't work,why?
thanks

Internally, the FTP paths include username, password and port details, which may be why.

I've made a note for us to take a look when we get a chance. We'll be more likely to if you link your account.

I open the ftp tab from Address Book of FTP sites.

however even if I directly open the ftp tab use the command of ftp://uname:pass@www.site.com:21,

the command
Go ftp://uname:pass@www.site.com:21 ExistingLister
Still can not work