Server no longer booting

I have a server with 3x2TB in Raidz1 as setup during install on a Proxmox 5.2 installation. It seems in the last couple of days it has had an issue an now no longer boots, and I am only presented with the grub recovery menu. I tried using zfsbootmenu to see if any of it was intact and it presented me with a pool that could not be imported (last accessed by a different system) but one good drive out of 3.
If I boot with drives 1,2,3 connected I get the same result. If I boot with drives 1,2...

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