BritBox Premier subscription through Apple TV doesn't work. Wrongly requires login

I have an annual subscription for BritBox Premier through AppleTV. It last worked on Tuesday. Wednesday I suddenly couldn't open it & it asks for email and password which I don’t have because AppleTV takes care of the sign on. I’m paying for both but not able to watch. I've been trying to resolve this for days. I've unplugged the AppleTV box; deleted the BritBox app and reinstalled it; both AppleTV & BritBox have up to date software; BritBox shows up in my Paid Subscriptions as paid until October 2026. I've seen comments saying to Restore Purchase. I can't find how to do that.

The BritBox login in screen comes up despite all of my efforts but I don't have an email or password. I shouldn't need one. Is there a way to contact Apple directly? Any help would be appreciated.