Hello @Mandsau 🙂
Just to be clear, are you using a Channel 4 log in and not your NOWTV login details?
Have you tried uninstalling and reinstalling the app?
I know lately some All4 apps have had problems (according to my PlayStation 3 app anyway.)
have you managed to fix this issue?
I have also had the same problem and nothing works; I deleted the app and then waited over a week in case it was a technical error needing to be fixed but still it says login error.
currently having this problem. Was there any solutions achieved?
Have you tried to delete and reinstall the app?
You could always unplug the router and device for a few minutes.