I'm suddenly seeing database connection errors such as
could not retrieve server_version: tlsv1 alert protocol version or
SSL error: tlsv1 alert protocol version (PG::Error).
As part of the frequent maintenances we run on our Heroku Data Services, and especially on Heroku Postgres, old, existing services are being migrated to new and updated servers that do no longer accept TLS v1.1 connections. Because of these maintenances, it's possible that your application starts seeing errors when connecting to the database if it was still using deprecated TLS versions.
Connections to these Heroku Postgres databases require using TLS v1.2 or v1.3.