Anyone successful hooking up a computer through a processor?

I'm not sure exactly what a NAD processor is but have you tried NAD tech support.?   

I would also check the computer BIOS.  https://10scopes.com/fix-motherboard-hdmi-no-signal/

I agree with Erik that there is a signal that isn't being generated or received to tell the computer the HDMI is connected but is being generated when it's unplugged and plugged back in.

No, the monitor is not beingshut off because I can source to other things on the nad processor no problem. 
 

When I boot computer with pc source preselected on the processor it will show pc screen? But when i switch from PC to something else and then switch to the PC it says no signal.
 

The switch convenience is absent and I have to reinsert the HDMI cable all the time.  I guess I could directly connect PC to the TV but I hate the LG operating system and lose the sound capability of processor.

Ahhh, that's an interesting clue.

So HDMI has a lot of handshaking going on.  It may be the order you turn on each matters.

Is it connecting right after you reboot the computer with the HDMI cable attached.  Have you checked your PC power setting to make sure it's not turning off the monitor.  There also may be a computer BIOS setting regarding video that could be checked.

I run a computer HDMI output from a video card (4k capable) into an input of an AVR receiver so I can watch content on Youtube and downloaded content.  Works great.  Can watch netflix and Amazon too.  I installed an 4k fanless video card in the computer.  

It's strange because every time I want to switch to the pc i get a no signal Display on the screen.  I fix it buy reinserting the HDMI cable, either side.  I have a really really good HDMI cable and a old one and they work the same in the situation.

Check the maximum frame rate you have set on output.  Processors may not be able to take mroe than 30 or 60 Hz