Whenever you create or update
package name
Make sure your package name is exactly the same [Upper case and lower case matters]
Do below step.
1). Check applicationId
in App level gradle
file,
2). Check package_name
in your google-services.json
file,
3). Check package
in your AndroidManifest
file
and for full confirmation make sure that your working package directory name i.e.("com.example.app") is also the same.
EDIT [ Any one who is facing this issue in
productFlavour
scenario, go check out Droid Chris's Solution ]