Hello,
On a fresh install of octopi I found that the ssh server had all of it's ssh keys filesizes to 0.
/etc/ssh/ssh_host_* files are all at 0 bytes in size.
To see this I pulled out a keyboard and monitor.
To fix it I wiped those files and ran
sudo /usr/bin/ssh-keygen -A
On other distros this usually is included in systemctl ssh scripts.
hopes this helps others.