Here's one for ya. My ipad 3 will play sound in certain videos but not others. It will not play sound in games or will not play any system sounds. Last night my son pulled up a video on facebook with his ipad 3'and played it with sound. Then I pulled the same vid up on my facebook and I had no sound. I downloaded a guitar app and found I get no sound. Same with Angrybirds. I go to Fox News videos and they play just fine, same with The Daily. I did a reset and it did not help. I did a full reset on Itunes and it did not help. Does anyone know what could be going on?
You've probably got the iPad muted. Normally mute only affects system sounds and alerts, but depending on how the developer coded the app it may mute those apps as well. I believe Apple offers guidelines to developers on what should mute/not-mute, but it's not always followed properly.
Muting is either controlled with the slide switch next to the volume buttons or from the multitask bar, depending on your settings.
iPad: Understanding the side switch