I'll confess up front: I really don't understand how this StackExchange website operates.
But, I created an account which I've mostly used in one StackExchange site and now I want to use it in another site. I'm trying to log in to the other site with my existing ID, but it says there's no account for my email address.
I've followed the instructions in this question: Can I have a common account across the Stack Exchange family of sites? I've clicked on 'Save and Copy Profile To All Stack Exchange Accounts'. But, that hasn't helped: when I try to log on to another StackExchange site, it still says there's no account for my email address. But, there is an account, obviously - it's this account I'm using to ask this question.
How do I use this existing account to log into a different StackExchange site?