Hi Norma, please take a look at this article: https://www.ca.com/us/services-support/ca-support/ca-support-online/knowledge-base-articles.TEC01000001613.html
Basically, it's because the user is already a user in another Agile Central subscription! Most likely he will have to login and change the username on that account (if he is a Subscription Admin) or have the Sub Admin of that other subscription make the change.
Thank-you. he does have access to another subscription so we will give this a try.
Retrieving data ...