Why does my created Amazon IAM user get "We can not find an account with that email address" when trying to log in?

In the Amazon IAM Management Console, I created a new IAM user, and assigned that user permissions and a password.

However, when an attempt to log in with that new IAM user is made via the Amazon AWS login page at https://console.aws.amazon.com/console/home, an error occurs:

There was a problem

We can not find an account with that email address

Why can't my IAM user log in successfully?

Amazon IAM users can't log in through the main Amazon AWS login page.

Instead, they need to use a custom login URL which is displayed at the top of your IAM Dashboard page. That link is labeled "IAM users sign-in link", and is of the form:

https://AWS-account-ID-or-alias.signin.aws.amazon.com/console

Using that account-specific IAM login form, the user should be able to log in successfully.

Reference: http://docs.aws.amazon.com/IAM/latest/UserGuide/id_users_sign-in.html