This is what i’ve done to get it up and running:

active the google api’s: (sign-up, follow the path mentioned in the short description provided by the module)

activated APIs:

Directions API (if I disable it nothing works anymore)
Geocoding API
Maps JavaScript API

then add this to your config.js:

{
            module: 'MMM-google-route',
            position: 'bottom_left',
            config: {
                height: '150px',
                width: '300px',
                key: 'your-google-apikey',
                directionsRequest:{
                    origin: 'city country',
                    destination: 'city country'
                }
            }
        },

Hope this works, did for me!