This happened when my sshd dameon did not start or died. You could use systemctl status to check it.

It has also happened when my white listed static IP for my machine that I access the server with changed. Do you have a default DROP policy?

Timing out indicates that either the sshd service doesn’t exist or is unreachable (but not blocked).

Check the dmesg for all sshd notifications and maybe you find why it is crashing (if the service is dead)