I can't connect my smartphone via Bluetooth.

The connection procedure may be the cause.
You cannot establish Bluetooth connection with your smartphone from the setting window of the smartphone when you use to connect Bluetooth headphones, etc.
In this case, a message such as "Pairing Unsuccessful" or "Couldn't pair with DDJ-200" is displayed.

Be sure to start the application before Bluetooth connection.
*You can't connect to a smartphone via Bluetooth automatically.