To fix it remove/rename the PID file. Find the postgres data directory. On macOS using homebrew it is in /usr/local/var/postgres/, or /usr/local/var/log/ other systems it might be /usr/var/postgres/. To make sure this is the problem, look at the log file (server.log).

PG::ConnectionBad - could not connect to server: Connection refused

To fix it remove/rename the PID file. Find the postgres data directory. On macOS using homebrew it is in /usr/local/var/postgres/, or /usr/local/var/log/ other systems it might be /usr/var/postgres/.
To make sure this is the problem, look at the log file (server.log). On the last lines you will see:
```
FATAL: lock file "postmaster.pid" already exists
HINT: Is another postmaster (PID 347) running in data directory "/usr/local/var/postgres"?
```

If so, `rm postmaster.pid`
Restart your server. On a mac using launchctl (with homebrew) the following commands will restart the server.

```brew services restart postgresql```

From  https://stackoverflow.com/questions/19828385/pgconnectionbad-could-not-connect-to-server-connection-refused