Question My motherboard isn't taking power from my power supply why is that?

[Coorious]

I recently bought a used gpu and plugged it into my system after i did that my system would not run anymore at first I thought it was a faulty psu so i replaced it but it still won't turn on. My motherboard has these leds on it and they turn on for a split second when I switch my psu on but then it turns off so now I think it is a faulty mobo please help.
Specs:CPU Ryzen 5 5600g
GPU none currently
RAM 16 gb 3200 mghz of corsairr vengeance ram
mobo asus prime wifi b550m
( I think that is everything that is important)

 

[DaronMal]

So with just power plugged in, all it does it light up the motherboard for a few seconds? If thats the case make sure to check all the cables, that they're all fully plugged in both on the motherboard and the PSU. If you're swapping between PSUs, please make sure to ONLY use the cables for the specific PSU you use, do not mix cables between PSUs.

you can try clearing the CMOS, might be a BIOS issue?

 

[Karadjgne]

Pull the gpu back out. See if it boots, you have a G series amd, so you should have no issues.

You bought a used gpu. It's possibly setup with a mining vbios, it's possibly bunk, there's no guarantee that it works at all, and yet the first suspect in a previously working system is the psu, followed shortly after by a faulty motherboard. Start with what's new to the pc, namely that used gpu, as the likely suspect.