Sorry for my stupidity, but I saw in the BIOS that it's set as "PCI" and not "PCI-E" that's why it's not working.

I don't know why it was set to that, I didn't even change it when I replaced my PSU.
Maybe when I reset the CMOS?
Anyway, I tried cleaning the "burn marks" and I was surprised that I was able to remove it.
At first, I thought it was burn marks, but then it was just like grease or something, I don't know how it ended up there, but it was all over the PCB.
And besides, I always clean my PC.