Remote Access NAS326

What is the result in your NAS in this page?

What did you set in router and NAS TCP/IP generial settings and Network Interface?
Can you post the screen here to check?
Normarlly, NAS can access internet and package installed, then it should be able to show in the list in zyxelcloud page and also router support UPnP, then able to control UPnP setting in zyxelcloud page. 

The second photo already told you the NAS doesn't find the UPnP router, you might need to check your UPnP setting.
If you still have problem with UPnP, that you only can setup port forwarding on your router.

for web port default is 80, but it might be collided to your router, so you can set 8080 and change your NAS http port from 80 to 8080 as your fourth photo.
But don't know what service you wuold like to use, but they should use the default port.as ftp port 21, ssh port 22 and telnet port 23 etc...

Ok so I had problems with the UPnP in the beginning also. I solved it like this:

IN THE ROUTER:
It seems that Zyxel NAS version of UPnP must match that of the Router UPnP version in order for it to "detect a UPnP router". What you must do is to:

1. Log in to your router as admin
2. Find UPnP settings (if you know your router supports UPnP)
3. See if you can change UPnP Datamodel version from 2 to 1

Note: For e.g. Technicolor router I this is under WAN services and I also had to press "show advanced" settings for it to show up. When I changed to the older version, my Zyxel NAS found my router as a UPnP router.

IN THE ZYXEL NAS: