My new GPU doesn't work. Am I doing something wrong?

I recently purchased a pre-owned RTX 4090 (Gigabyte Windforce). When I plugged it in, the fans turned on but I got no signal on the HDMI at all no matter what I tried (I tested all PCIe slots). Has anyone seen this before?

I was eventually able to connect both my old and new GPUs together and get video through the old one and what I saw was very concerning. Here are some screenshots. Note that I already tried deleting all my graphics drivers and re-installing from scratch with DDU. I have tried both positions of the Dual BIOS.

https://imgur.com/a/wdsY68v

In Sumary:

• GPU-Z does not detect the specs but shows the correct product ID.
• HWInfo cannot detect specs or vBIOS but also shows correct ID.
• Device Manager shows the GPU as having error 43.
• NVFlash fails to initialize it. The screen flashes for a second but it fails to dump or flash to that GPU.

My Specs:

• Motherboard: ROG B450-F Gaming (Old-ish, doesn't have the latest PCIe interface)

• Old GPU: RTX 2070 SUPER

• CPU: Ryzen 9 3900X (no video output)

• Power Supply: MAG A850GL (850W bought especifically for this new GPU).

The GPU seems legit and I have the original purchase ticket plus the serial is recognized by Gigabyte and is still under warranty.