I am getting this message but cannot locate under which account cloudflare is already activated for my website.
Its DNS history doesn’t ever show Cloudflare DNS, but it does show it was hosted at A2 Hosting for about a year. If that was you, check your A2 account.
If you have a Cloudflare account, open a ticket. You’ll have to click on any current domain, but note that the issue is for the new domain.