@borzel Indeed, the command
"xe vm-cd-eject --multiple" worked! All VMs now correctly auto boot on reboot/startup!
@Danp they are stored in a FreeNAS physical server connected to another physical hardware with xcp-ng. The link via iScsi.
Thanks. I guessed that I needed to put the full path on FreeNAS as there is not masking when expose as NSF by FreeNAS. So I put the full path as "/mnt/MybooksVolume/VM_ISOs" and that seems to have fixed the problem.