Firewall Certificate expiration in May 2022, update your firewall!
For more details, see the Update recommandation for SNS appliances in version 3.x before May 2022 article on the KB (authentication required).
SNS v3.7 LTSB
LTSB (Long-Term Support Branch) label
Major or minor versions with this label are considered versions that will be stable over a long term, and will be supported for at least 12 months. These versions are recommended for clients whose priority is stability instead of new features and optimizations.