エラーの発生内容

ActiveRecord :: ConnectionNotEstablished
PG::ConnectionBad: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?

やったこと

PC自体を再起動 → NGだった
psql -Vを実行
バージョンがpsql (PostgreSQL) 14.1
brew services listを実行
postgresql が error
tail -n 20 /usr/local/var/log/postgres.logを実行

2022-02-04 05:55:21.403 JST [4050] FATAL:  database files are incompatible with server
2022-02-04 05:55:21.403 JST [4050] DETAIL:  The data directory was initialized by PostgreSQL version 13, which is not compatible with this version 14.1.
2022-02-04 05:55:31.536 JST [4118] FATAL:  database files are incompatible with server

以下省略
:
:
:

解決方法

PostgreSQLのメジャーアップデートが原因で，データベースが読めないケースと推察。
以下を順に実行

brew services stop postgresql
==> Successfully stopped `postgresql`

brew upgrade postgresql
Warning: postgresql 14.1_1 already installed

rm -rf /usr/local/var/postgres.old

brew postgresql-upgrade-database
==> Upgrading postgresql data from 13 to 14...

省略
：
：

==> Upgraded postgresql data from 13 to 14!
==> Your postgresql 13 data remains at /usr/local/var/postgres.old

brew services start postgresql
==> Successfully started `postgresql`

brew services list
postgresql    started

やっぱり互換性が問題だったみたいですね；；
とにかく解決できてよかったーー。