Bugger. More testing last night and found a failed HDMI splitter. Only one month old. Anyway replaced it with another I had and all working again. NVIDIA CP has picked up the Yamaha Receiver and now I can extend displays etc.
I have the same issue. Has been running perfectly for some time and then I accidentally shut down the receiver first. Now the Control Panel will not find the HDMI source. Can not enable extend display as the device is showing unplugged and hence not recognised. have tried different start up...