Since migrating my NOW TV account to BT TV. I can no longer access NOW TV from my PC or iPhone. Ok from my TV via the BT TV box. The NOW TV PC app download link on the BT web page is out of date and appears no longer supported by NOW TV. Any attempt to change my NOW password via the NOW TV site receives 'Unable to reset password, please try again later'. Spent hours talking by telephone to BT support without success. NOW TV help desk unable to help as account now managed by BT.
There is no longer the need for an app to get Now on a PC or Mac; you just go to the Now website in the browser, sign in with your BT TV Now account details, and watch seamlessly. BT should have withdrawn these apps, as Now have done.
On a mobile phone or a tablet you still need the relevant app, though.
Third party Now accounts - BT, TalkTalk, Apple, Prime, etc., need to be maintained on the third party site, not the Now site. So BT needs to be making provision for this.