TNT Sports on Discovery+ doesn't work despite having a subscription

[fastfurious]

I subscribe to TNT Sports via Sky but can't watch any of the TNT Sports content (Premium plan) on my Discovery+ account.

I can only watch content from Eurosport (Standard plan).

When I try to watch anything from TNT Sports, I get this message:

On closer inspection, I seem to have two Sky subscriptions linked to my Discovery+ account.

Someone at Discovery+'s live chat seem to think that I have one subscription on Premium plan and the other with the Standard plan. It seems that the Standard plan link is preferred over the Premium plan link.

However, they said that Sky would have to remove this rogue link. But no one from Sky's call centre has been able to help me and get this resolved.

How can this rogue Sky subscription be unlinked from my Discovery+ account?

[fastfurious]

Here is a screenshot of my Discovery+ having two Sky accounts linked to it.