From long ago I have a Stack Exchange account with two site accounts: One for Stack Overflow and one for Software Engineering. Recently, after not using any of these accounts for years, I got a notification about a new reply to a post of mine on Stack Overflow.
However, when I click the notification that takes me to the reply on my own post, it doesn't let me reply, and shows "Join this community" in the corner, indicating I'm not logged in.
If I click "Join this community" I'm taken to a "Confirm new account" dialog that says it'll create a new Stack Overflow for my Stack Exchange account, even though my Stack Exchange account (as shown in the first image) clearly shows that I already have a Stack Overflow account.
How can I log into my already existing Stack Overflow account instead of creating a second (???) Stack Overflow account for my Stack Exchange account which already has one? What is going on here?