Question PC Won't Power on After Installing GPU

[plague_bat]

I have attempted to install a gpu on my PC. When pcei cable (6+2) is running to the psu, the PC won't power on at all, including mobo lights.

PC will power on when connected to the mobo without the pcei cable. Gpu gets lights but no fans and won't be detected by PC.
I have tried updating bios to latest version. The psu should be able to power the gpu. I've read the mobo may be limited to gen 3 pcei, but should still work for the most part.

Any ideas on what I can do to get the PC to power on and detect the gpu?

Mobo: msi b450 Gaming Pro Carbon
CPU: Ryzen 5 3400
GPU: Sapphire Nitro RX6600 xt
PSU: Seasonic Focus 550 Gold

 

[SyCoREAPER]

That's odd. Have you tried a different PCIe cable on and a different spot/slot on the PSU ? Cable seated properly on both ends?

 

[plague_bat]

That's odd. Have you tried a different PCIe cable on and a different spot/slot on the PSU ? Cable seated properly on both ends?

I'll try a new pcei cable. The one I'm using is an old one.

 

[KyaraM]

I'll try a new pcei cable. The one I'm using is an old one.

Old one in what way? Make sure to always use the power cables that came with your PSU, cables from different PSUs might not be laid out the same internally and can cause damage to your system!

 

[NaClKnight]

I know the 3400G comes with an iGPU so is this your first time trying it with a discrete/separate GPU?

Have you checked your BIOS for any relevant settings? Ensure that the video is set to auto detect instead of only using the integrated graphics

As mentioned before, only use PSU cables that came with the PSU or are confirmed to be compatible.

Have you tried a CMOS reset? i had a 5700 XT to that refused to POST in a new build until i cleared the CMOS

Are you getting any POST beeps from the motherboard speaker?