Question Monitor shows "No Signal" from GPU after taking out and reinstalling the same CPU ?

[TimyDanni]

Hello everybody! Yesterday I took my cpu out to clean it and apply new paste. However, after I turned the PC on, and plugged my HDMI to the GPU, my monitor was showing “No Signal Source”. Plugging the HDMI to the iGPU worked perfectly, but my GPU shows no signal. I made sure that I plugged in the 8-pin connector to my GPU, and a blue light is on the GPU when I turn in the PC. Wiggling the HDMI doesn’t help either. I’ve tried reseating the GPU, clearing the CMOS, I’ve tried another GPU, and none of those worked. When I check the Device Manager, my GPU is not showing up, and when I run AMD drivers, it says “Error: could not detect GPU”. Is my motherboard PCIe slot bad or the GPU faulty?

SPECS:
Motherboard: B75M
CPU: i5-2500
GPU: AMD RX570 4gb
RAM: 8gb DDR3
Storage: 1TB HDD
PSU: 550W (I don’t know the PSU model since this was a prebuilt and I also upgraded the GPU)

 

[rgd1101]

check for bend cpu pin

 

[TimyDanni]

Just checked, and none of the pins in the socket are bent

 

[TimyDanni]

check for bend cpu pin

None of the pins are bent. I've also tried 2 other GPU's that worked before this, and got no signal either.
When I checked Device Manager, i got error code 45 under hidden devices for the GPU.

 

[rgd1101]

that left with the motherboard issue

 

[TimyDanni]

that left with the motherboard issue

That’s what I thought it was, so I ordered a new motherboard. I’ll update you when I get it fitted.

 

[TimyDanni]

that left with the motherboard issue

Just replaced my motherboard with one of the same type, and now I’m getting no display. My GPU led is rapidly alternating between red and blue, and when I turn on the PC, all the fans slowly turn in the !get up to speed. The RGB in the fans also blinks very rapidly.