Esta confirmação foi feita num post colocado no fórum da Microsoft :

All pre-release product keys published earlier for builds of Windows 10 Insider Preview have been deactivated and will no longer activate any Preview builds, including Build 10240.  This will not impact any devices that were activated in the past using those product keys. We hope Insiders will continue to test Build 10240, which is only intended to be installed as an upgrade from a previously-activated version of Windows 10 Insider Preview – we do not support clean installs of Windows 10240.

Entretanto a Microsoft sabe que existem algumas falhas, pontuais diga-se, nos processos da ativação pedindo aos utilizadores que estejam nesta situação que aguardem alguns dias para realizar o processo de ativação.