Sometimes I get this error message in Proxmox after making a network change, messing with an ssh key, or some other random mistake. Once this happens, the nodes in my cluster become inaccessible through the admin interface. Here’s how I get the cluster running again:
Copy and paste the command that ssh spits out to remove the bad keys (if applicable)
Log in to each node and type:
pvecm updatecerts -F && systemctl restart pvedaemon pveproxy
The web interface should work again after a shift-click of the refresh button!