Optiplex 960 no audio device installed on windows 10

I got a cleaned up 960 from a friend who had installed win10 on it.  Everything was working great for about 4 months and then after a windows update - it went into a reboot loop.  I had to reformat and reinstall windows 10.  Everything is working again EXCEPT the audio.   In the windows sound settings, it says "no output devices found."

I tried downloading and installing drivers but it still will not find any sound output or input device.  

How can I get the audio working again?