Please see if any of these threads have suggestions relevant to your problem:
Headphones - Headphones showing working, but no sound at all
Sound
1 - Sound doesn't work
2 - No sound to speakers after kernel update
Please see if any of these threads have suggestions relevant to your problem:
Headphones - Headphones showing working, but no sound at all
Sound
1 - Sound doesn't work
2 - No sound to speakers after kernel update