I am also a Roku user, but I use the Roku 3, the only question I have to ask is this "have you registered and setup your Roku device on the Roku web-site before trying to use Now TV?"
If not then the Roku will not work.
Hope this helps.
I got the same error, after trying some of the suggestions here I realised it was because I had a new WiFi network and needed to select that within settings. If the error had been unable to connect to WiFi rather than login details not recognised it would have saved me about 24 hours of pain!
As I can't Edit my post I'll reply to it. I found a fix. When I installed the Roku stick it had an update, I think it's this update which stops NowTV from logging in. All you have to do to fix it is hold the reset button on the stick down for 15/20 secs and it will reset your stick to Default.
Now TV, now logs in first time and every time, only problem is you will need to setup all your other TV services again.
Hope that helps someone.
That was a good solution and, basically, the only one required when faced with a non-responsive device, i.e. a factory reset followed by re-registering the device with your details.
And also worth noting that a Factory Reset does not include removing updates, so your Stick is now running happily on the updated version you ascribed your woes to.
So your device might have been upset by the update process. But it clearly wasn’t upset by the contents of the update (unlike the recent iPad update that fubared everyone not on iPadOS 13).
Or it might have gotten itself upset anyway. All devices that fail, fail after an update, almost by definition. Question is, was it immediately after?
Hi again Roy
You said, "Question is, was it immediately after?". Well. the problem with updates is that we never know when they are going to be released, what they do when they're released or if they're beneficial.
The only thing we do know about updates is when something goes wrong, and only after an exhaustive check.