why has now tv blocked my stb app which has been working fine untill saturday
Sorry to sound ignorant, but what is STB?
Have you tried to delete and reinstall the app?
You could also turn off your router and device for a few minutes.
STB = Set Top Box 😉
What's the make and model number of your set-top box?
Haha couldn’t be more simpler and there was me thinking it was an app!
Leonard did say "app", and since STB is not a widely used acronym, your mystification is understandable.