One of our account users could not log in.
As the account owner I went to My Account > Manage users
I determined that they did in fact have a login for our account, however one does not log in with one's person name, or email address, one logs in with their "user name".
As the account owner, nowhere could I find out what that user's "user name" was.
To get that person to be able to get into CC I deleted their person name account and added a new one with the same information.
Please add an account holder's "user name" to the information provided on the "Manage users" page
https://app.constantcontact.com/pages/myaccount/settings/users
Thank you