Discovery Plus and TNT Sports activation ‘connected’ but not working in app

[Alex+R273]

I have recently moved from using a BT TNT sports subscription to a Sky TNT sports subscription and have therefore moved the Discover Plus subscription from BT to Sky.

However, having recently followed the online guidance for activating my Discovery Plus subscription via the Sky Shop. I have been unable to use my Discover Plus account. In the app it is asking me to sign up for a subscription even though this should have been activated via Sky. 

When checking Sky it states this is already active. I'm unclear on how to resolve this issue, as it would seem that the Sky activation has successfully connected with Discovery Plus. Help please.