Hi all,
I bought a NAS from Dlink dns-327L for general purpose of sharing photos, video clips and files. I use the wizard to setup the 327L. It connect to my asus router AC-87U.
Although I setup LAN, DDNS & port forwarding at network management and a multiple user in the "account manager". FTP server is enable also. I have not been able to access when used ftp. Did I miss something? 
Need some advise, thanks.
OK basics (but please remember I only have a 320L but I believe everything works the same)
You set up Dynamic DNS with one of those listed in the drop down menu on the Dynamic DNS and enabled it?
Can you also access the same address via web browser? if yes continue
Download and install FileZilla Client and use the same settings as you used via web browser - did it connect? If no FileZila will give a reason why it failed and from that info we can probably help more (hopefully).
Also have you Mapped the NAS as a network drive in your OS?