Google Maps Flutter - polyline does not show up on the map

Question

I'm trying to create directions/routes on the map but the polyline doesn't appear on the. Created new key without restriction, deactivated and reactivated the services: Roads API, Service Usage API, Service Management API, Stackdriver APIs, Street View APIs, Timezone API and even then without success.

https://i.sstatic.net/kHz9O.png

Answer 1

I don't know what it was exactly, I had to add the billing/payment data (on Google Cloud Platform ) and generate new keys one for Android app and one for iOS.