I have been grappling with this for a while - turns out it was something very simple:
grub-mkdevicemap -n
update-grub
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
done
Some other useful links for Proxmox setup:
https://pve.proxmox.com/wiki/Package_repositories
And to remove the "No Subscription" messages:
https://www.jamescoyle.net/how-to/614-remove-the-proxmox-no-subscriptio…