Can be due to missing an acceptable cipher on any one of the hosts.

This is a list of acceptable ciphers:

aes128-cbc
3des-cbc
blowfish-cbc
cast128-cbc
aes192-cbc
aes256-cbc
rijndael-cbc@lysator.liu.se
idea-cbc
none
arcfour128
arcfour256

These can be configured in /etc/ssh/sshd_config under Ciphers.

Try adding a supported cipher (aes256-cbc_ to the end of the ciphers in your ssh server config file. Note that SSH and OpenSSL ciphers are mapped, for example like the following:

// Maps the SSH name of a cipher to it's corresponding OpenSSL name
SSH_TO_OSSL = {
 "3des-cbc" => "des-ede3-cbc",
 "blowfish-cbc" => "bf-cbc",
 "aes256-cbc" => "aes-256-cbc",
 "aes192-cbc" => "aes-192-cbc",
 "aes128-cbc" => "aes-128-cbc",
 "idea-cbc" => "idea-cbc",
 "cast128-cbc" => "cast-cbc",
 "arcfour128" => "rc4",
 "arcfour256" => "rc4",
 "arcfour512" => "rc4",
 "none" => "none"
}