We're trying to integrate Marketing Cloud's Mobile Push with an existing Android app. Previously, our developers made their own implementation of Google Cloud Messaging (GCM) service and it works just fine, but when trying to do the same for Mobile Push the device is never registered in Marketing Cloud. Our developers are opting to keep the GCM implementation, but we want to know if it's possible to use both services at the same time within the app.
Is it possible to use both GCM and Mobile Push for sending push notifications? Is there any known issue regarding a previous implementation of GCM causing issues with the Journey Builder SDK and Mobile Push?