Mac Pro 5.1 no video after re installation

Hello.
I have a Mac Pro 4.1 flashed to 5.1. Single CPU.
Intel Xeon X5690 6 core
64 Gb RAM
Nvidia 720 (Kepler)
256 Gb SSD SATA

It was running Monterey win OCLP. Everything was fine until I tried to reinstall the OS. Now I have no video output.

I have tried with others GPU (5500XT, 5700XT, 6600 and original Apple GT12).
Also reseting PRAM, changing battery, removing RAM... Nothing.

I hear the booting chime. I think I am doing something wrong with the settings of OCLP.

Any ideas what can be?

Thank you in advance.

Author: @Original-Diver-2306