Suddenly, Can't connect to SSH server, Error fetching database list, Connection Population Error

Deane

I've been testing MySQL Compare and MySQL Data Compare which were working well for several days until suddenly I now get the below error message which I suspect is itself a potentially misleading error message. I'm hoping someone may have seen this behavior before and suggest what I might do to solve.

Clicking on Compare Now button produces . . .
MySQL Compare - Aborting
Can't connect to SSH server on 'xxxx.com':
Server does not support diffie-hellman-group-exchange-sha256 for keyexchange

Additionally, MySQL Data Compare produces the below popup message . . .
Connection Population Error
Unknown exception: Can't connect to SSH server on 'xxxx.com':
Server does not support diffie-hellman-group-exchange-sha256 for keyexchange

Clicking on the Database button to populate the drop-down list produces . . .
Error fetching database list
Error connecting to database
Can't connect to SSH server on 'xxxx.com':
Server does not support diffie-hellman-group-exchange-sha256 for keyexchange

Background:
1. I had previously been successfully using both MySQL Compare and MySQL Data Compare via their SSH user interface accessing databases residing on 2 separate domains/machines.
2. Now neither program can connect to SSH server on either of the machines and now produce this error.

I'm hoping someone may have seen this behavior before and suggest what I might do to solve.