PC Help

Long story for understanding....
I built a PC about three years ago... went on vacation, unplugged it, but did not unplug the internet cable... came home, started it up.. black screen.... changed vid cards.. black screen. plugged into mother board.. black screen.. fans started, but no video... it sat another year, then I needed it, so I ordered a mother board,,, installed it.... no fans nothing... mother board lit up, but nothing will turn on??? Okay... power supply must have given up... took the power supply from anpother rig, installed... same thing.. nothing on power up. mother board lights up with the led's... for the hell of it I put the OLD mother board back in... no fans nothing, it just lights up the led's no clicks nothing. tried hitting the start switch on the motherboard.. nothing... put the new motherboard back in, changed the cables, checked the memory, installed it in another rig, worked fine... still nothing. I get no clicks, no fans nothing happens when I turn it on... power supply is plugged in to the board correctly... By getting down CLOSE when i push the on button I can hear a faint click in the power supply..... I tested old power supply in my good machine.. works fine. I swapped out everything from the good machine to this motherboard, memory all of it... did not replace the processor... nothing still... very faint click when powered on. no fans, just the motherboard LED's... its an Asus Prime Z270-A with a 7700K processor... Not sure where to go next.. replace the processor.. but even with a bad processor shouldnt the fans turn on? Thanks for any tips or advice!
KP