Hello there,
When I first finished building this PC, I booted up my PC to find out that it wouldnt post and the BIOS speaker said that it was a GPU error. I then tried the same card in the second slot and the PC worked fine. Suspecting a dodgy motherboard, I returned it and I got a new one however, after rebuilding, I had the exact same issue but this time the pc would get to the screen where it prompts you to enter the BIOS but when I press F2, the PC would show a black screen and the fans will start to ramp up.
Attempted troubleshooting steps
Bios update
Limiting the the port to Gen 2 (this is the only way the PC would even show an image)
SPECS
Ryzen 7 2700x
Asus Strix B450 E
GTX 750ti
16gb 3200mhz