CPU not detected or failed

Gaming Scr0b

Reputable
Jul 8, 2015
3
0
4,510
Specs:
i5 6600k(used)
16gb ddr4 ram 2400mhz
evga gtx 970 sc
evga b1 750w psu
msi b250 gaming pro carbon
nzxt s340

So I have decided to upgrade the parts of my computer, the cpu, ram, gpu, and motherboard. The motherboard and ram are brand new while the gpu and cpu are used. After completing the build, I ran into a problem. My computer did not post anything. On my motherboard, there is a ez debug led, and it states that my cpu is not detected or working. I have tried re-seating the cpu many times, checked if there are any bent pins, and check if all the cables are plugged in correctly many times but sadly no luck. I have also tried the tom's hardware guide. Sadly, I have been without the use of my computer for over a month, and it is stressing me out. Any suggestions? Should I buy a new cpu and return it?