We had a similar situation on Sunday that might be related to this. One player was unable to hear the Jukebox sounds (running Windows and Chrome in Google Hangouts). When he took off his headset he found that they were playing through his speakers on the other side of the room. Much head-scratching ensued. What I assume was happening is that the Roll20 app is transmitting its audio separately from the voice and video being handled by Google Hangouts, and so although this player's Hangout audio was configured correctly for his headset, the Roll20 app was playing through his Windows default settings, and so to the speakers. In the post above, the OP's game was using Skype to handle voice, and Roll20 to handle the game, so again it's possible that the Skype voice was configured to come to the player's headset while the jukebox audio was going to his speakers (possibly switched off).