Your email address is not linked to a Yahoo ID.
↑ If you encounter this error when you try to join any Yahoo! Groups using the web interface, it means your Yahoo account is somehow not associated with any Yahoo ID (firstname.lastname@example.org). It doesn’t matter if it’s the same email address you’ve used for Yahoo Groups for 15 years. It doesn’t matter that you’ve been receiving emails from the Yahoo! Groups email list without any problems, your account is somehow not recognised by the Yahoo Groups web interface. In fact, the groups that you’ve joined doesn’t even show up under “Groups”. I believe there’s a broken link between legacy accounts and some of the newer Yahoo systems.
Yahoo! Groups membership wizard. This wizard will help you claim accounts that somehow slipped through the crack. If you have any unclaimed memberships, you need to match the old email with the new email. Even if the old email is exactly the same as the new email, you still need to match.
Once done, you will have access to the Yahoo! Groups web interface again. It should not affect any of your existing email list functionalities