How do I configure a PostgreSQL monitor on 11.5

I have set up the following for the monitor I am configuring: Monitor type: PostgreSQL Parent Monitor: postgresql send string: select true; receive string: t user: password: Database: Alias Addresses: any Alias Ports: 5432

I use these same settings from a PostgreSQL shell on my MacBook and I get the expected return character "t". The F5 monitor fails. why is this?