Hey Dannykana,
Make sure you’re going into the Project Settings and turning on Play Services as well as the APK Packaging for Android. You need to make sure you are using the Play key that you created for that specific application, not one of your other applications you may have already released.
Here are some additional links I thought may be helpful to you:
- [ APIs for Android][1]
- [Adding Licensing to your App][2]
- [ Play Licensing Service][3]
- [ Play Developer Console][4]
Thanks!
https://developers…com/android/guides/overview
[2]: http://developer.android.com//play/licensing/adding-licensing.html
[3]: https://support…com/googleplay/android-developer/answer/186113?hl=en
[4]: https://play…com/apps/publish/signup/