K-Series; firmware 7.31.02.0008, 7.31.03.0010, 7.31.04.0002
Enabled SSH access to system management ('set ssh enabled').
Then, upgraded firmware from 7.31.04.0002 (or lower) to 8.02.01.0012, and rebooted onto it.
The non-default 'set ssh enabled' command is no longer present ('show config ssh').
Design differences in NVRAM format prevent the pre-upgrade SSH state from being read post-upgrade, defaulting it to "disabled".
Rather than upgrading to 8.02, upgrade to firmware 8.11.03.0005 or higher.
After the fact, use telnet or serial console to re-add the missing command.
To prevent such configuration loss, use the CLI in order to boot onto firmware 8.02.01.0012 with the refreshed configuration.
show config outfile slot11/.cfg
set boot system K-80201-0012
Reboot to new code?
Reboot and reload config?