SSG550M was EOL'ed more than two years ago and last day to convert warranty to a support contract was January 31st 2017 - getting it done now is unrealistic.
If its a SSG550 (non-M) it was EOL back in 2008.
(Ref: https://www.juniper.net/support/eol/ns_hw.html).
Best hope is to re-register your hardware to yourself and hope that JTAC as a one-off will provide latest recommended software for the platform.... but I would't count on it.