I just ran into this issue after activating a new secondary card and trying to attach it to my account (this was the #2 Google result for this issue for you necropost criticizers), and when I contacted Discover support, they said:
"Because every account must have a unique user ID, each account must be registered separately for the Account Center."
OK, but I'm not trying to have multiple accounts under one username. I'm just fine having one account with one username with one email address, which both card's notifications have been going to.
"We don't currently provide the option to combine more than one account under the same user ID. You can, however, use the same password on more than one account."
OK, but I'm not trying to combine multiple accounts under one username, nor have I ever heard of using the same password on multiple accounts being a problem (
So they either misunderstood the question, have gotten "card" confused with "account" (you can have one without the other), or they're trying to tell me I just can't have two cards on one account.
What bothers me about this (besides the fact that every other bank I've had multiple cards on lets me do this) is that I now have to sign into discovercard.com with two different usernames and have to use possibly two different email addresses... I don't see how this makes any sense.
Oh, and if you're of the "account means card and card means account" logic (meaning you have to have an account for each card), here's how Discover contradict that: After activation, I got the same prompt PlyrStar93 posted in their screenshot showing the "I have a Discover Card account" option; this means you don't have to have an account to activate the card, and if you've already got an existing account, you don't have to have a card to have an account.
The fact that it would then block you from attaching the card to the account because you've already got a card on the account directly contradicts the prompt "I have a Discover Card account" if it only works if you don't have a card on the account!!! What is a "Discover Card" account without a card???
Yes, I did fill out all of the prompts that I saw; and even if Discover makes you fill out all of your personal information again (non-pre-filled or pre-filled after some wonky hoop-jumping), the process is nonsensical no matter how you cut it.
Since I see no options to add another card from my account, I'm completely putting this regressive way of doing things on Discover; they shouldn't be sending card offers for people who already have cards if they require we create a completely new account with a different username and a different email address. They should be the ones with the horse and buggy logo but upside down if they can't have two cards on one account and consider a "card" and an "account" to be the same thing, which they obviously allow to exist completely separately from one another.