Vm wont boot

I've change my hardware to an i3 processor platform. All works fine.
Happy to hear!
An old AMD cpus platforms are dead for Proxmox :)
OVMF is only a specific part of Proxmox VE, not everybody uses. If issues for old hardware can be fixed, we're glad to do it (example). Unfortunately, we don't have such old hardware around, so we can't debug the issue here and apparently nobody complained to upstream OVMF/EDK 2 developers yet (without a reproducer we can't).
 
Recently I've done fresh install on Dell Z90D7 - newest proxmox i HA and everything worked fine. No downgrade was needed.
It was just last check after changing to new machine.