Exactly the same with me...
but the longer story is:
Had BT internet 5 years ago, since left, then got BT again, so one BT id had two accounts assigned to it. Created a new BT ID as in its current setup it wouldnt let me even subscribe to discovery plus via BT. The new ID brought over the current active account only and I was able to sign up.
Signed up last Saturday. No email to activate. On the phone for an hour to call centre as well. Get the email (they resend it), click to activate discovery+, just goes to the My BT landing page. TNT sports is listed as a product I own next to my broadband and I can click manage, but when I do it says to progress the order and asks for the account id which is selected, I click next and just end up on a Sorry please contact customer services.
Sunday they raised a support ticket to a higher up team, havent heard back.
I can access TNT via the BT sports app on both my phone and playstation 5, but I've never been able to progress to the link page to link this TNT offer with an existing or otherwise discovery+ subscription - which of course I want for my LG telly and to watch in 4k.
