I can't set [AUDIO] in the rekordbox Preferences correctly.

The installation of the driver software might be incomplete or the connection might be causing a problem.
If you’ve already installed the driver software, try again using the following procedure:

■Windows
1. Close rekordbox and disconnect the DJM-S7 from your computer.
2. Open the control panel (or [Start] > [Settings] > [Apps]) and uninstall [DJM-S7 Driver].
3. Close Windows.
4. Disconnect other USB devices, USB hubs, etc.
5. Start Windows.
6. Download the driver software from [here].
7. Install the driver software again.
　*An error will occur when the license agreement screen is displayed and you try to proceed without clicking "I agree".
8. Connect the DJM-S7 to another port without using a USB hub, etc.

If you still can't set [AUDIO], the problem might be caused by operating system settings, etc.
See case 3 and 6 in the guide [here].

■Mac
Follow the instructions in the guide [here].

If you still experience the problem, it might be caused by operating system sound settings, etc.
Remove all other USB devices from your Mac, uninstall the virtual audio device etc, and restart the Mac.