@LeeA it may be that the fix is not 100% yet. They will be doing tests at Now Towers to make sure it is working properly.
There is a bug with the latest software pushed out by NowTV.
Have you tried pressing the back button a couple of times on the NowTV remote or another possible work around is press the Sky Store button on the remote, then press the Home Button to see if that clears the error message.
I don't get that message myself, but i am encountering other bugs and glitches with the new NowTV firmware 😠.