Append +01 (example+01@gmail) if you see the same error "A user with this email address already exists on the team" to your email address. I found that when entering the password for sandbox account it must contains a capital letter, number and punctuation mark other wise it will give an error and does not locate the error posting. So please change your password to this formate as well.
Topic:
Developer Tools & Services
SubTopic:
Xcode
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