From
man sshd_config:
ChallengeResponseAuthentication
Specifies whether challenge-response authentication is allowed.
All authentication styles from login.conf(5) are supported. The
default is “yes”.
From /etc/ssh/sshd_config:
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no
And the error message doesn't ring a bell, unfortunately. Does the ssh.com client allow you to specify a protocol?