Netflix App on the nowtv software 8.1.3 worked first time for me.
So i don't know why software 8.1.3 is not working for you, perhaps the Netflix error is common to one particular ISP and Router brand ?
My ISP is NowTV with the Hub 2 Router with the std black box connected via Ethernet.
Perhaps members who are on software 8.1.3 on the black boxes who can't open the Netflix App on their devices could post their ISP to see if there is anything in common related.
I initially had the same error, NW-6-400, when trying to load the Netflix app. I updated to 8.1.3 4149, i then hit update again and it initiated another update for apps (didn't specify which ones), now Netflix works just fine, i have been watching it this afternoon. I have a Nowtv black box connected via ethernet and my isp is talktalk. Hope this info helps.
My Netflix version is 4.2 build 90618035.
I've read this thread and don't know what else to suggest, after i updated my Nowtv box Netflix worked straight away. I hope you and everyone else with this problem are able to resolve it quickly. Fingers crossed.
I’m having the same problem with the same device. It works on the now tv stick but not the box. I have rang Netflix and told them about the same code. It’s not an internet issue but sounds like an issue with the box. Hopefully they’ll fix it soon!
I've done as suggested
Updated, 5x home, 3x ff and 2x rw hidden app updated.
I was already up dated before I tried this so no changes made.
Have reset router, unplugged Now TV box and restarted it.
App still has code NW-6-400 error. Netflix app just does not work on Now TV black box.
Back to watching Netflix via Amazon Fire Stick for the time being for me.