[NoOne]

check volum control this is a win 7 pic, but somethign simiilar will exist in win8/10. also, look for a button that may be hiding what you can see.. a per app volum should be viewable one way or another.

it remembers the last setting, so if it was muted last time, it remains that way until you revert it back. some programs can take exclusive control too... i happen to be listenign to music with a program that does such a thing.. wasapi... doesn't allow any other program to make a peep. there's a check box in "sound settings" or "audio device" settings somewhere that will prevent programs from taking exlusive control... if oyu find it try both settings.