Have you tried to open a VM console at Proxmox VE web UI and get this error?
More probably you have a host authentication issue… maybe you reinstalled a PVE node or changed IP addresses, so some nodes have outdated host identification, so they not trust each other.
The way to solve it is quite easy… following steps found at https://forum.proxmox.com/threads/task-errors-failed-to-run-vncproxy.90746/.
Imagine from node proxmox-05 you cannot access proxmox-02 (with IP address 192.168.1.12) VMs consoles, then just run these steps:
# Forget previous host identification (replace node name)
root@proxmox-05:~# ssh-keygen -f "/etc/ssh/ssh_known_hosts" -R "proxmox-02"
# Now connect to the other node via its IP address (replace node name & IP address), accept new node authenticity
root@proxmox-05:~/.ssh# /usr/bin/ssh -e none -o 'HostKeyAlias=proxmox-02' root@192.168.1.12 /bin/trueThat’s all.
