There appears to be a bug with UPnP within some routers that doesnt allow the MBL to create a UPnP entry for itself. Even though on the MBL GUI, it says “Port forwarding connection established”, it might be showing this in error.
If your router has UPnP enabled, then disable it and within the MBL GUI select “Manual” connection method and then manually forward the two ports (80 & 443) to the IP Address assigned to your MBL. Always ensure your MBL has a static IP Address (either by assigning it via its MAC address in your Router, or select “Static IP” from within the MBL GUI).
I had the same issue a while ago, and it took me a while to find the cause and resolve it. You have to be sure you forward the ports within the router after disabling UPnP otherwise the MBL will resort to a relay connection (via WD’s servers).
This issue isnt very well documented, but WD did admit to this problem a little while ago. It is admitted in this post:
http://community.wdc.com/t5/WD-Mobile-Apps/Device-Offline-not-accessible-message/td-p/323079
HTH.
