I'm also having this error having just set the stick up today.
I've attempted to uninstall Netflix, reset Netflix, reset internet connection, unplug device, unplug internet and reset the firestick to factory default.
The error code is ui-800-3.
Netflix is working on other devices in my home.
Any help would be much appreciated.
Also having the same trouble. I pressed home x5 , fast forward x3 and rewind x2. This took me into a page full of codes , mac address etc and gave me the option to update soft wear, i thought this would work. It didnt for me but it might for you.
Just an update, the error still persists and nothing has worked.
Still no response from NowTV although they have stated this is an error with Netflix (which is strange seeing as though I can access Netfllix in my home on other streaming devices).
I'll give it a few more days and if no response I'll be returning the stick for a refund.
It's a shame but I only bought the stick to stream Netflix to another room without the need of buying a smart TV.
Somebody over on the Roku Forum who had no success from the Netflix trouble shooting guide and found that using their Roku on a different wifi network temporarily to access the Netflix App worked for them.
The way they resolved it was to use their smartphone has a wifi hotspot.
More info here
Might be worth a try if the error is still showing on the Netflix App.
I've heard nothing back despite raising it also with Now TV twitter and online chat. This will be 2 weeks ago tomorrow.
It doesnt appear as though they are taking the issue serious, despite numerous users having the same problem.
As I've previously mentioned I only purchased the stick to watch Netflix on a TV upstairs so the lack of help with Now TV is very dissapointing.