I am also trying to install Proxmox 6.2-4 and I am having the same problem. I have already updated the BIOS of my HP Z400 to the latest available version 3.61 Rev.A, but the problem remains.
The GRUB screen appears and after selecting the installation option, it starts loading drivers, waits for DHCP packets and then, after receiving the IP address, the screen goes out and everything is black. Then the monitor displays a message that the resolution is not supported.
From all I researched, it seems that the problem is related to the video card and monitor set. Apparently, it tries to load a video configuration (the one where the mouse starts to work and the proxmox license appears), but the monitor does not recognize it. It uses an old NVIDIA Quadro 2000 1GB graphics card that has a DVI type video output, but my monitor has a VGA input, so I use an adapter.
I have six HP's Z400 to install the Proxmox and I'm getting worried ... Everyone uses the same video card and I had planned to install the Proxmox but this little problem in the installation is frustrating me.
These machines were running on Windows 7 pro, the system I'm replacing with Proxmox. When I use HD with Windows 7, everything works fine on my monitor. But to install Proxmox I am not getting it.
Any idea?