No Audio Output Device is Installed

Hello,

I know this question has been asked a lot in the past, but absolutely none of the solutions given seem to be relevant to me, so I figured I'd attempt to ask again to see if something will come up that I can actually use.

I have Inspiron 15 5567, using Realtek 6.0 audio driver. 

I've had no problems with audio whatsoever until recent updates from Dell and Windows. Then, after restarting my computer, the audio is unavailable, with the message "No Audio Output Device is installed" (sic). I found that weird, but I figured something must have been incomplete with the update, as there was a pending firmware update to Dell. So after restarting my machine, the firmware updated, and the audio was fixed. NOTE: The audio at that point started working again. However, after a day or so I just happened to put my computer to sleep (not even restarted, just asleep), and when I woke it up, the audio was off again. The message "No Audio Output Device is installed" was back, as it is right now.

This machine is relatively new, I purchased it back in January. Between that and the fact that the audio output magically turned on and then off again, I'm pretty certain there is absolutely nothing in terms of hardware that could be an issue, and as such I have not yet attempted a BIOS diagnostic. 

It is worth noting that my computer has two operating systems on it: Windows 10 and Ubuntu 16.04. This exact same issue is mirrored on both OS at the same time. Therefore, the issue must somehow lie with Dell. 

The first thing I have tried is to re-install the audio driver. When I look up the Windows Device Manager, this is what I get:

There is no audio driver listed, enabled or disabled. Furthermore, there is no "Other devices" category, either. 

When I tell either Device Manager or Dell's support page to automatically detect missing drivers, it says all my drivers are up to date. Uh, what?

When I use device manager to install the audio driver manually (making sure to select the correct one) I get this:

Needless to say after it automatically restarts, the Device Manager still doesn't list any audio device. 

When I use Dell's Support page to install the driver manually from there, the PC restarts normally (without a deadly blue screen), but the result is exactly the same. No audio device. 

What do?