I am trying out the new Firebase/Crashlytics setup and seem to run into a weird issue.
I came across this issue in the new Firebase SDK upgrade to 17.0.0+ version.
The issue was caused when we use multiple flavors. In case you are using a separate flavor - debug and have it linked to firebase as well, instead of adding the google-services.json file to the app root, we have to add the flavor specific json file to the appropriate folder for the flavor - app -> src -> (flavor folder).
This will ensure that the generated code has the correct client id for the flavor.
This is a silly mistake but there are chances for people to miss it.