Official comment
First, you don't need to use the internal mixer in rekordbox, you have it configured for external use.
Second you don't have the audio outputs configured properly. Output deck 1 should be on CH1, and deck 2 should be CH2.
In order to configure it to record in other software, you'll need to assign the inputs to 5/6 as those are the only ones set to the REC. If you want, you can reconfigure it for 1/2 to be REC, which may be needed as some applications don't support ASIO.



