HA suddenly unreachable and rebooted by itself

Suddenly, I cannot reach HA, from internal network. It is HA OS running on Proxmox VM.

I logged into Proxmox, checked the HA VM, it was online.

I clicked Console, and saw the black screen “connecting” or something, it was booting up.

Once booted up, I saw this in the Proxmox summary:

So, something happened, but I don’t know what.

I checked HA, Settings, System, Log, but nothing.

Any way to check this? Which logs?