(1) Have you ever updated the BIOS? What version is it now? I would go for it.
(2)
(a) Did you see this at the LucidSound LS25 site...?...
https://lucidsound.zendesk.com/hc/en-us/articles/360004054313-Microphone-not-working-in-Windows-10
Microphone Not Working In Windows 10
It says, look at the privacy settings, at "START, Settings, Privacy, Microphone".
(b) Here's another...
https://lucidsound.zendesk.com/hc/en-us/articles/115003242973-LS25-Microphone-not-working
LS25 Microphone not working
It says, check that the mic mute button is not in effect.
(3) "Audio has never, ever registered on this pc"
That's bad. It's another indicator of a hardware problem. Why didn't you return it?