iPad volume sliders gone, volume not working

The volume on my mom's iPad 3 (running on iOS 8.2) has recently stopped working. The speakers still work - alarms and the Siri tone still play - but apps that use volume (iTunes, etc.) no longer produce any sound. The volume buttons on the device don't do anything, which would lead me to suspect a hardware issue, but the volume sliders are also mysteriously either missing or greyed out in the Control Center and relevant apps. For example:

In iTunes, instead of being missing outright, the volume slider is present, but greyed out:

I have tried resetting the device, to no avail. I'm hoping I don't have to restore the device to factory settings. Any advice?