Still I would make some remarks.I can't quite understand what you mean.You say that you have connected the NUC to the Zone 2 of the AVR with a HDMI cable.
What is the purpose of this ?
2 - Then you have another cable - RCA to 3.5mm cable to Zone 2 of my receiver.What's the purpose of this cable ?
3 - then you connect "the cable" (which one) to the NUC mic / headphone port, I see a Realtec window open .
4 - you say then there is no sound.But I don't see you mention from which source the audio should come !!!
Are you trying to get the source audio from the Zone 2 via the HDMI ??
And via the same Zone 2 , you also have the 3.5mm jack plugged to the audio card input on the NUC.
I'm not so sure if this will work.On one hand you use the HDMI interface > going to the NUC (I suppose also a HDMI interface input).
And then you also have the RCA/3.5 mm jack cable , from another Zone 2 jack (input or output ?), going into the NUC's audio card.
Have you confirmed that you get sound out of the Zone 2 via the HDMI ?Is the sound coming in the NUC ?If it's not coming in the NUC , then what is the purpose of this connection ??
No sound in to the NUC , will obviously give no sound out to the AVR !!
Furthermore is the Realtec soundcard in the NUC working ?Have you checked this ?
You use Win 10 - there were some issues with W 10 in that it was installing the wrong drivers for some devices , or it was disabling some devices.
You could try to re-install the Realtec drivers (also see if it can do better with W7 or Vista drivers).
Try 2 different ways.Uninstall the card - Reboot - install the (new) driver.See if your card is working.
Uninstall the card.Shut down the NUC - take out the sound card if it's a separate device.Boot up and install the new drivers.
Shut down - put the audio card back in - re-boot and let it search for new devices.
Or it may automatically find the new device and install the new drivers.
Technics SP-25/SME3009IIISMkI/ADC TRX-II/mounted
on massive grey marble(43kg)/2nd SP-25/SME3009IIIS
MkII/DL103(43kg)/Denon PRA-1000/PRA-1500/Pow Amp
POA-1500/Luxman M-150 classic1975)/PhonoPre ProjPhon
BoxSE2/Speakers IMF TLS-80MkII/CartsDL-160/ADC XLM