Lights are on, software says no device. It's almost always the USB chain or a missing driver — and testing in the right order stops you reinstalling things for nothing.
USB cables die silently and charge-only cables look identical to data cables. Use the cable that shipped with the unit, or any cable you've proven carries data (it shows up as a device, not just power).
Cheap unpowered hubs and monitor USB ports drop DJ controllers constantly. Plug directly into the laptop. If you must use a hub, it needs its own power supply.
On Windows most Pioneer DJ / AlphaTheta controllers need the dedicated driver from the official support site; on macOS newer units are class-compliant but the Setting Utility still unlocks routing. Download only from the manufacturer's support page — never a driver site.
System Settings → Privacy & Security: some setups need microphone permission granted to the DJ app for its audio engine. If macOS asked and you clicked Don't Allow, the app can see the controller but not hear it.
In rekordbox: Preferences → Audio → your controller as the audio device. In Serato: the controller must be on the supported list for your plan. If the software sees the controller but there's no sound, this is the missing step.
A controller is two devices in one cable — a MIDI surface and a sound card. Detection failures are the USB layer; silent-but-detected is the audio-routing layer. Splitting it that way tells you which half to fix.
Fixed it? The manual this came from covers the DJ controller the same way — every control, every failure mode, in plain English with diagrams. The Complete Rig — all four guides — £39, instant PDF.
Get the manual → £39 Or keep using the free stuff →