Open device manager > click view > show hidden devices > manually expand all rows > look for any row displaying a yellow triangle with black exclamation mark or unknown device > post an image into the thread

Look in each:
Audio inputs and outputs
Sound, video and game controllers
for Conexant High Definition Audio Driver.
If this is not yet installed then download and install:
Driver - HP EliteDesk 800 G3 Small Form Factor PC | HP® Customer Support

Download and Install HP UEFI diagnostics Windows (right upper area of this link):
HP PC Hardware Diagnostics | HP® Official Site

Launch the application > click component tests > check audio playback > run the test (it may take a few minutes to play) > report the results into the thread

Run the system extensive test overnight.