Like so many others here, i was having problems with my gen 3 not seeing network storage. Everything else including my gen 1 wdtv live could all see the nas fine and can play the media from it, but the new gen 3 could not see the nas.
I think i managed to sort it in my case so thought i’d share. My nas is a qnap 659 so it may be slighly different depending on your model.
But i saw some posts reguarding the local master browser been an issue. and i did find a checkbox under advanced settings under microsoft networking settings in my qnap’s menus called called local master browser. I unticked it and now suddenly my gen 3 can now see the nas folders under network shares where it wouldn’t before i unticked the box.
Hope this helps