Saved: Proxmox Linux Header updates caused boot failures

I have been grappling with this for a while - turns out it was something very simple:

grub-mkdevicemap -n

root@pve:~# grub-mkdevicemap -n
root@pve:~# update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-2.6.32-39-pve
Found initrd image: /boot/initrd.img-2.6.32-39-pve
Found memtest86+ image: /boot/memtest86+.bin
Found memtest86+ multiboot image: /boot/memtest86+_multiboot.bin

Some other useful links for Proxmox setup:

And to remove the "No Subscription" messages: