What is wrong my laptop's sound? again?

A simple long shot, but did you try turning up the volume from the keyboard?

@seperate_reality Yes, But it still doesn’t work.

Did you try youtube? You get visual, but no sound?

Another simple long shot is to check and make sure you don’t have mute on.

Don’t know where you went, but reinstall flash player, media player and if still no go, I would reinstall audio driver.

I’ve tried Youtube, and I’ve check from Control Panel > Audio devices to make sure it’s not mute. I never mute my laptop, it’s still fine yesterday.

Have you tried restarting it?

Yes, many times but it’s still the same. Last time when it happened I let it for a few days and it worked again. And now it starts to cause a problem again. If there’s something I could do I’ll do it right away.

Have u tried reinstalling/updating the audio driver as @seperate_reality said?

What about rebooting? What drivers are you using, and what is the model of your computer?

What sort of computer and what operating system?