Chris

That error code means the specific device you were using is not registered with BT Sport, not that you’re not registered as a BT Sport subscriber with BT. You would still have been able to watch the Liverpool match on a device already successfully registered.

Registering the app for a service is usually part of setting it up when you first install it. You could try deleting and reinstalling. The method apps use to register differs from app to app, but typically they will present you with a unique code the first time you start them up, and give you a URL to enter in a web browser. You enter the unique code on the web page and that has the effect of linking your account with the specific instance of the app that you have downloaded to your device.

Again, I’m not saying this is definitely your problem but it is an example of a problem BT customer service can’t fix for you as you have to initiate it on your app.