That link works to log into your Reservation account (different from your Registration account), but the resulting "My Account" link (and the "Logout" link, both displayed near the bottom left of the following screen) cannot be seen on some small-screen browsers.
In these cases (when the My Account link is not visible), AFTER you login
successfully, this link can be used to get you to your account:
http://www.nissanusa.com/leaf-electric-car/dashboard/index
(it is .../leaf-electric-car/dashboard/...)