iGPU Passthrough to Windows VM but no DP output

[inf4m3z]

Hi all,
I set up my proxmox server as described in this tutorial to passthrough my Intel 630 to my Windows VM:
https://3os.org/infrastructure/proxmox/gpu-passthrough/igpu-passthrough-to-vm/

The Windows device manager shows the Intel 630 and the newest driver is installed:


But if I connect a monitor to the server via a DP cable, no image is displayed.

Does anyone have an idea what could be causing this?