Why don't my volume does not work !!!
Assuming the volume switch is on, it might be a software issue.
Try backing up the device, and restoring as new according to http://support.apple.com/kb/HT4137
NB: set up as a NEW device because a software issue will be in the backup. If the issue persists after restoring as new, you should offer the device for service.
Retrieving data ...