Add my-app.firebaseapp.com (my-app is unique identifier of your Firebase App) to the HTTP referrers in the Browser-Key Credentials from the Google APIs console.
https://console.cloud.google.com/apis/credentials?project=my-app
Add my-app.firebaseapp.com (my-app is unique identifier of your Firebase App) to the HTTP referrers in the Browser-Key Credentials from the Google APIs console.
https://console.cloud.google.com/apis/credentials?project=my-app