Boot failed Not a bootable disk

Hi all:

One of my VMs in my Proxmox 5.4 cluster stopped working after a stop / start.
Yesterday the VM was working just fine.
I have tried to restore the VM to another storage (from weekly backup).
Backup was done on 27.07 and 3.08 and the machine was working on 4.08.2019.

After the restore (with both versions) I still get the same error: boot failed, not a bootable disk.

Any ideas?

Thanks
Vlad