Bill, could this be your problem?

https://wiki.x2go.org/doku.php/doc:faq:start

Known Issues

Can't login to x2goserver with an ECDSA key

Currently, older versions of the ssh library used by X2Go called libssh are unable to work with ECDSA keys. However you may use an RSA key - if you need to - or go with the SSH default authenticating method using the remote user's password.

SSH Login issue

If you already use OpenSSH to get a shell on your x2go server, you may get this message when trying to connect with x2go:

The host key for this server was not found but an othertype of key exists. An attacker might change the default server key to confuse your client into thinking the key does not exist This is related to the ECDSA host key (related to the previous FAQ entry - although there is a subtle difference between host and client keys.) To solve this issue, you can disable ECDSA keys on your OpenSSH server configuration, by commenting the following line in /etc/ssh/sshd_config file:

#HostKey /etc/ssh/ssh_host_ecdsa_key Then restart the SSH service. Now you should not get the error message anymore.