Maybe... how many sound devices you have? I mean output and connected ones, like HDMI sound on graphics card, sound from motherboard, USB sound device, others...
Also installing pulseaudio
you can see what's set as default, and change it.
I had this kind of problem in the past, because some apps were always using my nvidia sound in HDMI, and not the one I use, setting it in pulseaudio solved my problems.