Error: The default Firebase app has not yet been configured

[neeact]

Hello,

we are not able to use this plugin for authentication in iOS because it looks like the system cannot set the database address correctly.

We have put the GoogleService-Info.plist file into the root directory (same level as the config.xml) but the console log in XCode shows "[Firebase/Core][I-COR000003] The default Firebase app has not yet been configured. Add [FIRApp configure]; (FirebaseApp.configure() in Swift) to your application initialization. Read more: https://goo.gl/ctyzm8."

It looks like the user is authenticated (we use authentication via custom tokens) but it doesn't have access to the database (Firebase throws the error "permission_denied ... Client doesn't have permission to access the desired data")

Can you please explain where should we put the .plist file to identify the correct database?
Thank you so much!!!