Because there is no License Key for Explaindio Elements Free Footage Module. Activation works with login of your Explaindio Membership account inside the software.
Simply enter your Explaindio Member Account Sign-up Email ID / Username and Password inside Settings of your Explaindio Elements Software, Close Settings, Create a new project, add a scene and click any of the asset panels i.e. try adding a video. Free Footage Module icon will be added on your Explaindio Elements software within few seconds.