Did you ever get this resolved? I'm having the same issue, and support isn't responding to me.
Just for additional info, the "this email address is unavailable" error comes as soon as you click anywhere outside of the email update box, and because of the error the "save changes" option is grayed out. Also, while I want to add my work email to my account, I've discovered that attempting to enter my other personal email address, or even a friend's email address as a test, results in the same error.
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