if you receive an email telling you about a friend invitation, but don't
follow the link in the email, it can be hard to figure out how to accept
the invitation! likewise with inter-member emails.
It turns out that, once you're logged in to your account, there's a gray bar at the very top of the page with links to your inter-member email - the envelope icon - and friends - the person icon. click on the person icon to see if you have any invites from other members pending.