Users that have previously migrated their username to an email address will see the following message. For instance, if you were previously a TruckersEdge/MembersEdge/Express subscriber you will have been migrated to an email address. 

Proceed by signing in with the email address provided and the password.  If you do not recall what this password is, click  the Reset password button and an email will be sent to you which will allow you to reset your password.