sendNotification status:301 Response:Error=DeprecatedEndpoint
Google deprecated GCM, the GCM server and client APIs were removed on May 29, 2019. Now, Google supports Firebase Cloud Messaging (FCM), which inherits the reliable and scalable GCM infrastructure, plus many new features.
There is a setting on brainCould Portal page, at Design | Core App Info | Advanced Settings - Compatibility Settings section, please ensure the [ ] Use legacy GCM for Google Push Notifications is unchecked, if you are using Google FCM on you app.
Otherwise, you will get this pushing notification error from brainCloud server for pushing notification API calls.