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When i try to register account on 4ancient, register problem is "* The username is already in use!".. When you try anoher nick, e.g "qwszxcsd123"" it does the same
as Xuki suspected above, this is an error you get usually when you are trying to create an account with an already in-use email.
Please attempt to create an account with a free e-mail and your desired username. It should work normally.