Did you already try to flash your Edison? It might be a corrupt image so flashing it would solve it. Is this only happening with SSH or with Serial too? To connect using SSH is necessary to have a password set so this won’t be an option. Also, do you get any error message? If so, please paste it here.
If you’re unsure on how to flash your Edison, check this guide: https://communities.intel.com/docs/DOC-25154.
Take a look at this thread too: https://communities.intel.com/thread/62536.