[Wordpress issuses] mickaelcdm on "Activation link"

Hello,
My friend try to create account 'floriancdm'.
It's impossible to validate the account.
When he click in the activation link in the email that said "That username is already activated."
And when he try to sign in that said "Your account has not been activated. We sent you an email with a link to activate."

How to solve it ?

Thanks.

.

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