This can happen for 2 reasons: either you had previously registered on ICO Engine, or your address is already registered on our system.
If you fall under the first case, worry not! You will simply have to login using your ICO Engine credentials. Your ICO Engine account has been transferred in EidooID. This means that you are already registered and, also, the verification level achieved in ICO Engine will also be applied to your EidooID account.
If you fall under the second case, once again there can be 2 reasons: either because you had previously registered on ICO Engine (see the paragraph on top), or you have registered on EidooID with a different email. Make sure to input the correct credentials to be able to login.