Using v4.0.10 of Pushsharp (nuget package), I am getting error GCM Authorization Failed when sending push notifications to Android devices.
Seems the bug raised in issue 574 (https://github.com/Redth/PushSharp/issues/574 ) has been compiled into the nuget package, yet I'm still getting this error.
Could this be related to the introduction of Firebase Cloud Messaging?
Does anyone still have success using GCM?
As of right now, GCM is still usable. However, it is highly encouraged for new users to use FCM instead. Either way, for both GCM and FCM, you must use a Server Key generated from the Firebase Console. There is a visible note in the GCM docs saying:
Starting from Sept. 2016 new server key can only be created in the Firebase Console using the Cloud Messaging tab of the Settings panel. Existing projects that need to create a new server key can be imported in the Firebase console without affecting their existing configuration.
The Authorization error has been encountered by number of users, some also had an old project. See my answer here for more details.