Laptop headphone jack produces no sound

The headphones are detected, because when they are plugged in, they appear in the sound settings.

The problem is that they just don't output any sound.

Laptop speakers output sound just fine.

I'm running Ubuntu 16.04 x64

This is the output from running alsa-info.sh:

http://pastebin.com/1aDcq86B

What steps can I take to try and debug this issue myself?

Edit 1

Thanks to @Rexford and this answer, I've worked out how to get detailed debugging output from pulseaudio, by temporarily modifying /etc/pulse/client.conf using the --log-level flag.

I'll report back after I play around with this new information and try to find the problem.

Edit 2

Woke up this morning planning on getting to the bottom of this issue, when I discovered that the sound from the headphones started working.

Last night I had tried many solutions (from various forums and webpages), but was not restarting my computer (was just doing pulseaudio -k && sudo alsa force-reload).

So I guess that the reboot was necessary to make one of the solutions kick in and actually work.

One of the biggest things I tried was uninstalling pulseaudio, installing gnome-audio as a replacement and going back to pulseaudio. So I recommend others try that if they are struggling. Just note that if you do that, you should follow the instructions here to get your volume/sound icon back (if it's missing after reboot - which it was for me).

I can't get to the root of this problem now, because it no longer exists for me.

Edit 3

The problem came back...

Debug logs from pulseaudio don't reveal anything useful (e.g. error messages).

According to this diagram, alsa is the next stop to check for the cause.

Solution 1:

This answer appears to be working for me, but I have not investigated why yet.

To repeat the solution, just run this command in a shell (no root needed):

alsactl restore