Linksys EA7300 FTP Server, not being able to remotely access its files

[cainn]

I just bought the Linksys EA7300,

And I have a USB 3.0 Portable Hard Drived attached to its USB 3.0 port on the router, I have enabled the FTP option, set a new username and password, I can access the files locally (When I am connected to the same home network) but when I try to access it via the Internet (Remotely) I am not being promted to enter my usernam and password to gain access to my files

Anyone knows what would caused this issue? Is it something related to my DMZ settings in my Sonic's provided router?

Thanks in advance