Notebook Audio

Gifted our nephew's wife with an HP Envy x 360 laptop in the summer of 2017.  Early this past summer the mute light lit up and there was no sound.  Nephew did a system restore and problem solved.  Later in August the same thing happened...restored again and once more problem solved.  Two weeks ago it muted again and won't unmute.  Restore was again tried...no luck.  I now have the computer and did a full system recovery twice....no luck.  Diagnostics show no problem...in fact during the diagnostics there is sound but the volume drops steadily until it once again mutes.  Took the laptop to our local computer repair shop...they did full recovery twice...no luck again.  I'm frustrated...I'm fed up...and if this laptop has to be replaced, which I'm willing to do, but it most definitely won't be replaced with another HP!  I've searched online and have discovered MANY other of the same audio complaints by other Envy x 360 owners.  Any suggestions other than to just walk away and look for another brand.