I'm aware there are a few other discussions on this subject but none seem to give a clear-cut answer. I'm trying to help my brother-in-law active the Discovery+ app that he recently added to his Sky subscription. To apply the 6-digit activation code it appears that he also needs an account with Discovery+ which he'll have to pay for which makes adding the product to his Sky package rather pointless. Should he be able to use his Sky account email/password details to login to the Discovery+ app in order to apply the 6-digit PIN?
[This might be a red herring but I read somewhere that sometimes Sky continue to associate an old email address with the Sky account i.e. have Sky transferred an obsolete email address/password to Discovery+? This was certainly the case with me a few years ago on a completely unrelated issue when I tried to change the contact phone number on my Sky account but the email address I routinely used for my Sky account was not the "primary email address" that Sky held for the account and thus did not have sufficient authority to make the change (I had to call the Support Centre for them to change the phone number associated with my account).]
