Official comment
@Madeleine > The driver security disable function is only available within 30 minutes of installing the drivers. If you tried to disable that before installing the drivers, you wouldn't see it, and the process would not have completed properly. Please try the following:
1) Download and install the drivers.
2) After the installation has completed, disable the driver security.
3) Install the drivers again immediately.
Restart your computer and now the device should become available within rekordbox.