Problem booting OVH/kimsufi headless server / HELP!

Currently the only way for me to access my server is to use rescue cd with some kind of debian.

Hardware config of server is similar to what kimsufi offered.

After restarting server “from hard disk” all I get is response to ping, all ports are closed.
When I use nixos-enter and then nixos-rebuild boot I don’t get errors. Running grub-install /dev/sda does not give any errors. fsck is clean on all filesystems.
journalctl --last-boots does not show any entries for failed boots - only some old boots that did not fail.

What can I run from rescue cd to actually get any kind of info?