Proxmox NoVNC failed to connect to server & failed to run vncproxy (SOLVED)

Ran into the issue where the Proxmox WebGUI console will not connect to a host. The strange thing was that it would work for some hosts but not others.

Reseach on the Internet suggested that the source of the issue could be:

Web browser - cleared cache, tried multiple browsers.
DNS - systems were not resolving correctly. Updated DNS servers and resolved DNS resolution issue.

Neither of this worked for us.

Found this article:

Proxmox failed to run vncproxy - Here is how we sort it out

Proxmox failed to run vncproxy error occur due to improper symlink configuration. Sometimes invoking the vncproxy can resolve this error.

BobcaresKeerthi PS

which suggested that the source of the issue was ssh authorized_keys was not properly linked to /etc/pve/priv.

Our file was linked properly and we discovered that there were multiple entries in the authorized_keys file for each host in the cluster. This was also the case for /etc/ssh/ssh_known_hosts.

We suspected that vncproxy was getting confused by the multiple entries.

We resolved the issue by:

Logging into each host
Clearing out the ssh_known_hosts file
Manually ssh to the other hosts in the cluster

Fortunately for us our cluster is small, just three nodes. I think it could be a nightmare if you had a large cluster.