"This account is already registered in the system" error means that this account is already in use by another user. We only allow duplicate accounts with paid subscriptions (not the FREE one).
Please subscribe to our Unlimited subscription plan and let us know when it is done, We will have to allow the account manually.
Off course, all the trades that you have opened manually in your account will not be linked to the trade copier. The trade copier will just ignore the manual trades.
You can also close a trade that has been opened by the trade copier. In that case, the trade copier will just consider the order as closed.