What playback device are you using ?
Where the NowTV Bonus Streams is available for Championship Football matches on the Sky Red button service when using a full blown NowTV monthly Sports Pass on certain NowTV playback devices.
Here's some more information about Bonus Streams.
NowTV have missed off the NowTV boxes (Freeview NowTV Smart box doesn't currently offer Bonus Streams) and NowTV Stick from the below list which i copied & pasted from one of their guide articles.
Got a Sky Sports Month Pass, and one of the devices listed below? You can access extra channels on selected sports events using Bonus Streams, including additional EFL matches and F1 Race Control.
You’ll find all available Bonus Streams at the bottom of your NOW TV app homepage. Don't worry if you can't see any Bonus Streams right now – they'll appear automatically by the time the event starts.
Keep in mindYou can’t access Bonus Streams with a Sky Sports Day or Week Pass. NOW TV Boost features, including full HD and 50 frames per second, aren't available on Bonus Streams.
A link from the bonus streams section.
When a Bonus Stream is available, you'll find the option at the bottom of your NOW TV app homepage.
Keep in mind
You can't watch Bonus Streams with a Sky Sports Day or Mobile Month Pass.
So I would assume it would not work with the week pass since they are no longer selling these as freely as before.