If you had provided just a username then it means that the username is at our free Discord community here (if you already have an account there)
During authentication, a bot named tadmainbot will send you the authentication information there as a private message. Read that message, and copy the e-code in that message, and return back to TAD to authenticate yourself.
From version 6.9.1.45 onwards we also allow users to register at other communities that are compatible with TAD. In such a case you would have given the username there as <username>!<c-code> For example; if your username at that community is hclinton and its code is pqr, the username specified by you would be hclinton!pqr
Currently, the list of communities compatible with TAD are listed below:
More communities may decide to adhere to the TAD specifications for authentication. If you have a community of your own which you want TAD to authenticate with, email us at sabu@teamtad.com and we'll send more details on how to achieve the compatibility.