Question New setup: GPU is not detected at all in pcie 4 x16 slot and not functioning correctly in pcie 4x2 slot

[NotLisztening]

Mobo: msi MAG B650 TOMAHAWK WIFI
cpu: Ryzen 5 7600x
psu: 530W
gpus: rtx 2060 (and gtx 760 to troubleshoot)
ram: 2x16 ddr5 (optimized for intel&amd)
os: win 10 (on a 1tb m.2)

Hey, I'm at the end of my wits. Today I upgraded my mobo and my cpu (and ram and ssd).
I have already installed the newest bios-drivers and updated msi, amd and geforce-game-ready drivers.
I have also cleared cmos and did a clean install of bios-firmware.

When i plug my gpu into the main pcie, the small led on the gpu itself turns red. When i plug in the power-cable it turns white, but it does not post when I turn on the system.
The gpu-fan does not start spinning, the gpu-rgb does not light up and the system can only run on integrated graphics. (Neither the mobo, nor windows recognize a card)
I also tried my gtx 760 with the same result.
I have also tried using a different 650W psu with the same result.
Both cards work fine in a different system.

When i put the gpu into the lower pcie 4x2 slot I could get an imagine and the system recognizes the card.
However, the gpu-fans only spin for about 5 seconds on max during boot-up and never turn on again. (the gpu-rgb however stays on)

I recently repasted the rtx 2060, but the result was the same with the gtx 760, so I don't think that's the issue.

Does anyone have an idea what else I could try to troubleshoot?
Or is there a way to know whether there's a problem with my mobo or my cpu?
(I bought the cpu used)

 

[rgd1101]

fresh os install?

 

[NotLisztening]

yep :/ but the issue happens before windows loads.

fresh os install?

 

[rgd1101]

return the cpu. try a different one

 

[SkyNetRising]

Check cpu socket for bent/broken pins.

 

[NotLisztening]

I did, it looks alright. Though I doubt the am5 socket to be easily damaged. I ordered a different motherboard and will check if that resolves the issue

 

[hotaru.hino]

I did, it looks alright. Though I doubt the am5 socket to be easily damaged. I ordered a different motherboard and will check if that resolves the issue

LGA type sockets have always had the complaint that they're really easy to screw up. Those "pins" are like <1mm thick metal tabs.

 

[NotLisztening]

LGA type sockets have always had the complaint that they're really easy to screw up. Those "pins" are like <1mm thick metal tabs.

I just realized that I completely ignored one possible source of this issue: the mobo has two 4+4 eps connector slots, but my psu only has one plug. I read online that one can transmit 300W and that this should be plenty. Is it possible this is causing this?