Thanks for the quick response!
I am not trying to use the same email. I replaced this email with another so the first can be freely used on a new account.
So if you try to replace the email from the account editing section, the system just adds up the new email to your profile instead of replacing the old?
If that is correct, now I have 2 emails associated with this account, the one I firstly registered and the one that I tried to replace the first one with.
