FLX4 left deck won't play sound through laptop speakers

I am using laptop, headphones, and have Pc Master Out on, and the Cue button under Master levels is also on. Right deck plays as supposed both for cue and master, but for some reason, only cue works for the left deck, there's no sound on laptop speakers. 

Microphone is allowed on all apps. In settings, defauls system sound is on Realtek and for rekordbox app it's Line. I tried reinstalling the app too. All knobs are turned to the middle. What am I doing wrong?