UK streaming service NOW TV currently incompatible with new Apple TV 4K [update: fixed]

Update: The company has released a new software update and this issue has now been resolved. To update to the latest version of the NOW app, search for NOW in the App Store on the Apple TV 4K and press the Update button. (You can alternatively wait for the system to update the app automatically.)
NOW (nee NOW TV) is one of the leading streaming services in the UK, offering access to Sky channels, TV shows and movies. Although the NOW TV app has never been the leading example of quality on tvOS