APK validation fail and unable to merge manifests

I'm trying to upload a GearVR app to the Cculus store. When trying to validate it, I get the same error as this post: https://forums.oculus.com/developer/discussion/41190/apk-validation-failed ;

The problem is that I've followed all the steps to fix it mentioned in the post but it still doesn't work. After I've modified and copied the AndroidManifest.xml file to Assets/Plugins/Android I get  the "Unable to merge manifests" error when I try to Build the APK in Unity.

I'm using Unity 2017.1.0f3

Does anyone have any suggestions as to what might be happening?