Notebook Audio

I upgraded from Windows 7 to Windows 10 several weeks ago.  This appeared to be successful, and I haven't used the laptop until now. I find that I have no sound output.  The speaker icon has a red cross at the bottom, and when I hover the mouse over it, it says "No speakers or headphones are plugged in".

I have gone through the advice on both HP and Microsoft sites, tryigt the various things suggesed and none of these work.

I went to Device Manager, where there is "AMD high definition deivce".  When II ask it to update the driver, it tells me that the best driver software is already installed.  I have tried uninstalling it and restarting the computer, and it is unchanged.  I have tried installing a driver manually, selecting the High Defition Drive - it completes this, but my speakers are still "Unplugged".

I downloaded the HP hardware diagnostics program, and ran it to test the sound, and the speakers successfully made the appropriate sounds so it passed the test. So the speakers are apparently plugged in!!

I assume that the problem is that there is not a Windows 10 driver for my sound processor.

I cannot roll back to Windows 7 as I have passed the four week period.  I did not get any system disks with the laptop (it does not have a CD/DVD drive) so cannot get back to Windows 7 that way.  I tried to get the Media Creation Tool from Microsoft, but when I entered the product code,  I got the message:

"The product key you entered appears to be for software that was pre-installed by the manufacturer.  Please contact the manufacturer for software recovery options"

I can't find any way of contacting HP to ask about recovery options.

Is there anything else I can do or am I stuck with a laptop with no sound?

Any help appreciated.