the step before a restore is to back up your information.
Are there any symbols showing? i.e. paired with bluetooth possibly?
Check your volume settings of course, check your mute switch, try using speaker phone during a call and adjusting the volume with that on.
Is this only under certain circumstances, i.e. making a call or when doing anything? have you tried listening to music?
Hi Bob/Nicki4023, I have the same problem, it lost sound completely, but the mute switch is off. The switch seems to be working since it visibly turns to mute when applied. Music visibly starts playing but no sound is emitted, and the volume slider is not shown unless I plug in the headphones, then the volume buttons start working again and the sound returns but when I unplug the headphones it turns mute again. The same happens when playing a video, videos that played normally yesterday today seem like no sound was recorded. Apps i.e. games don't emit any sound although not set up on mute. The ringtone sounds when receiving a call but the rest of notifications would just vibrate even having a programmed sound. I'm starting to think this might be a virus... Please help