If you are using a Mac you need to update to 11.6. If you cannot the fix is;
The fix: in the terminal type the following command:
sudo xattr -cr (and drag the folder containing the audio files behind it) then press the return key
repeat the above step with all folders where audio files are stored.
sudo (=run the command as admin) is not strictly necessary, but can fix some other issues as well.
Once done resync the USB stick and the CDJ's should now see the tracks in the playlists