The authentication endpoint Kerberos was not found on the configured Secure Token Service! - Redux

So today I had an interesting moment of Deja vu today, where we started getting this issue again.

This time though, the configuration had already been done so it was a bit mystifying to say the least and to further add to the confusion, it worked on one server but not the other.

After a lot of blood, sweat and tears the issue was tracked down to the affected server being unable to communicate with the ADFS load balancer. In essence, our network guys had not opened the firewall for both servers but just one of them.

So, if you get this issue, it might simply be due to a good old fashioned network issue.