How to restore factory config on SSR device
From:
https://www.juniper.net/documentation/us/en/software/session-smart-router/docs/config_basics/#factory-default-configuration
From SSR PCLI
run the command "restore config factory-default"
followed by "commit"
Note: this option resets ssr configuration to factory configuration file, it does not wipe the entire system.
Alternate option
re-image device from USB stick
https://www.juniper.net/documentation/us/en/software/session-smart-router/docs/intro_installation/