iPad app speaker sounds not working

HI I recently bought this ipad air 2 64gb wifi + cellular, and updated it to ios 8.4.1. Last night I used earphones for the first time since my roommate is studying. When I unplugged it, I played my games but there are no sound from the speakers. I can only hear them when I put the earphones back. I've tried playing from Spotify and youtube, the sounds work just fine (basically when I'm force playing them). I've already restarted the ipad but same thing happens. Help pls? I'm still under 7-day replacement policy so I'm not quite sure if this is grounds for replacement. Thank you so much for the help!