qemu exited with code 1 - GPU passthrough attemp

Hello,
I've been trying different solutions for my GPU passthrough to work, but my VM with the PCI passthrough doesn't start. The only error in the CLI is start failed: QEMU exited with code 1
The GPU used is an Nvidia Quadro P400
I've followed and tried solutions in the following places:
https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_pci_passthrough
https://pve.proxmox.com/wiki/PCI_Passthrough
https://pve.proxmox.com/wiki/PCI(e)_Passthrough
and passed through a...

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