Headphones/Speaker issue with DDJ FLX4

I bought my son the DDJ FLX4 for xmas and subscribed to Rekordbox via IOS Iphone connection. Tried many options/watched many tutorials but still have no sound through headphone jack and speakers only work via Bluetooth not line-in connection? IOS doesn't offer preferences tab to change the settings only the Audio tab to switch between Split Output or not. Tried using a splitter cable off the phone but still nothing. This all seems a far cry from a plug n play system. Just going round in circles!