πŸ€ͺ F**K YEAAAHHH! Finally solved it after a day - JSON data not displaying after initial deployment on Heroku. Had to use `heroku pg:reset` and `heroku pg:push` from local dev db to heroku remote db. Hell I have a headache now πŸ€• but at least I have a production Rails JSON API in return - https://railsapi-booklist.herokuapp.com/books