Audio problems: No input or output sound

[Ackers2021]

HP Envy x360 laptop - no input or output sound.  I've tried lots of things to try to sort this out, including:

Realtek High-Definition (HD) Audio Driver installed/updated

Audio Diagnostics say:

-  No speakers found' (Hardware problem detected)

-  No microphones found ("  "  ")

Realtek(R) Audio Properties says 'Device not started ....'

Event viewer says:  MS-Windows-Kernel-PnP Event 411

Skype is one example of where I can't hear the person I'm talking to and they can't hear me.

Very frustrating I can't solve the issue after 10+ hours trying everything suggested on MS site and HP site.

It might be an issue created when I upgraded to Windows 11 in November?

Or I have inadvertently ticked/unticked a box somewhere?

Below are the results of some of the checks I have made

-  Realtek(R) Audio Properties:  - shows the Speakers are indeed installed and Drivers updated:

-  HP Audio Check - Diagnostics:  says:

    -  'No speakers found (Hardware problem detected)'

    -  'No microphones found (Hardware problem detected):

How do I solve the 'hardware problems detected'?  I have carried out checks, but same message keeps appearing

-  In the 'Event Viewer' results: 

    -  Several occurrences of the same Error message have appeared in the 'Device Manager - Realtek(R) Audio' window over the last few days: 

    Event source:  Microsoft-Windows-Kernel-PnP;  Event ID 411

    Q:  What is 'Event ID 411' and how do I sort it out?

Any suggestions how to resolve the sound issue would be much appreciated.  Thanks in advance.