Perform all the configuration following a video tutorial, as url of the site explain that it should be: link .
However, trying to authenticate generates the following error.
I think I've had this problem and it's because Facebook has no way of accessing your local environment, so you have to have a public url so you can access the callbacks.
A simple option is to install ngrok and then bin the rails port to a public address by running:
ngrok http 3000
Then the address that shows you in the console (which will be of type http://2d265ad4.ngrok.io ) you add to your facebook settings.