I have an app that started in eclipse. The package name starts with a capital, and it always compiled and installed correctly. Now that I have moved the project into android
In Android Studio rename the package name and in build.gradle leave old applicationId. Although your project's package name matches the application ID by default, you can change it. You should never change the application ID. More: https://developer.android.com/studio/build/application-id.html#change_the.package_name
Had the same problem with capitals in old package name. In studio simply rename the package in build.gradle (Module:app) from com.abc.example to com.ABC.example sync the project and all should be well.
Maybe google play is not case sensitive and thats why it doesn't recognize the upercase package name, you might be able to post an update with the same package name but lowercase. Have you tried it?