Moved my email hosting over to outlook.com and having trouble with one email address out of five

I successfully moved over the email hosting for 5 of the email addresses on my domain. But one address will not work. 

-I was able to add it as a member account through www.domains.live.com/‎ just like the others. 

-The microsoft account existed before(just like the others) because we had to create accounts when logging into windows 8. 

-After adding it as a member account I couldn't log into outlook.com or any other Microsoft site with that user name. All the other worked fine.

-The username and password still work to log into the Windows 8 machine she works on. 

-Wont let me recover the password. It says that the account doesn't exist. 

-When I try to create the account I get the following error: "This email address is part of a reserved domain such as live.com, hotmail.com, or msn.com. Please enter a different email address."

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Any thoughts on how I can resolve this issue?

Thanks!