Question GPU not recognised but seems to be powering fine

[Sindenization]

I have just replaced my PSU, CPU cooler and GPU. I tested the system with the iGPU once I put the new CPU cooler on and it was working fine. When I plugged in the graphics card it boots up to a black screen. I tested my old GPU in the system and I'm getting the same fault, despite it working before.
The GPU is getting power, fans are spinning and LED is on. I tested my old power supply and it's not working there either. So it's not the GPU or PSU.
I don't think it's the motherboard either as the GPU appears to be communicating with the PCIe slot. Without being plugged in the fans and light don't work.

The BIOS is set to PCIe as the primary graphics adaptor, but even with the GPU plugged in, only iGPU works.
I tried downloading the NVidia drivers, but it says No GPU detected.

It's an ITX system so no beep codes or LED codes.


Mobo: ASRock Z370 Fatal1ty itx
CPU: 8600k
Cooler: Cryorig C7
GPU: Gigabyte 3070 Eagle OC
PSU: Corsair SF750

Old GPU is the r7 260x, which isn't working now either.

 

[Nemesia]

Did you plug your monitor in the GPU port and not on the motherboard port?

How were you able to test installing the Nvidia drivers if the GPU does not give you any signal?

Meaning you're using the integrated graphics and the monitor is plugged in the integrated graphics and you're trying to install the GPU drivers? Won't work.

 

[Sindenization]

Did you plug your monitor in the GPU port and not on the motherboard port?

How were you able to test installing the Nvidia drivers if the GPU does not give you any signal?

Meaning you're using the integrated graphics and the monitor is plugged in the integrated graphics and you're trying to install the GPU drivers? Won't work.

I plugged the cable into the GPU yes, but it was black screen so I plugged it a second cable into my motherboard and that was working.

I tried installing the drivers on the iGPU, but if that won't work that's fine.
In my device manager neither the old or the new GPU shows up when I try to use them.

 

[dotas1]

Since both cards are not working now, my guess is that you got either a bad power supply, or a damaged PCIe slot.

 

[Sindenization]

Since both cards are not working now, my guess is that you got either a bad power supply, or a damaged PCIe slot.

Tried the old power supply, no luck. But in doing so, when I put the new PSU back in it started working. I haven't a clue what has changed, but I'll take it.

Unfortunately no solution for if anyone in future has the same issue.