I can watch now tv through my bt box, but the moment i try to watch via another device, like it says i can, nothing works. However, it says that i can't as they don't recognise my email address, and it's the only address that i have and use. Please help
Does it not say which e-mail address to use on the activation email you received from BT? If not try using your BT ID
If you login to your bt account. Under Now TV you should able to manage your subscription and change your password via that.
This should help you login to the app.
I have used this method before