Help! Can't adjust the volume of my ipad 2 - volume button not appearing

Hi. My ipad has no sound - especially when playing music. The volume button is just broken (not the one on the side but on the music app itself) - I can't adjust the volume, the round thing to adjust it is just gone, and it's just gray and no sound at all. But when I ask Siri/adjust the ringer, there's still a sound. So I don't really get it.

Even when I plug in the earphones, there's still no sound and I still can't adjust the volume
The volume buttongs on the side doesn't do anything

I tried reseting my ipad

iOS 7.1
iPad 2