Hi Gustavo,
I fixed the issue by doing the following:
Make the changes to your android manifest file from the following docs page:
https://docs.mendix.com/howto/mobile/setting-up-native-push-notifications#customize-android-manifest
If you did that and it still does not work, make sure that the security for your “NativeNotification” entity are set properly.
You will need create rights and read/write rights for the notificationGUID.
I hope this helps!