Cant hear skype calls when minimised

Hello,

I just brought a Hp Pavillion 15 Notebook (Windows 8.1), and its been working fine. Ive been in a skype call with my friends while playing a game (meaning skype is minimised). But all of a sudden, the sound stops and i can hear my game, but not skype. I maximised skype and then my friends could hear me and i could hear them, but everytime i minimise skype i cant hear them and they can't hear me. I tried this with spotify, and i could hear the music even when spotify was minimised.

If someone could help me find a solution to this so i can play games and hear skype while minimised, that would be great.

Thanks.