A Push Credential is a record for a push notification channel, for Android this Push Credential is a push notification channel record for FCM or GCM. Push Credentials are managed in the console under Mobile Push Credentials.
Whenever a registration is performed via Voice.register(…) in the Android SDK the identity and the Push Credential SID provided in the JWT based access token, along with the FCM/GCM token are used as a unique address to send push notifications to this application instance whenever a call is made to reach that identity. Using Voice.unregister(…) removes the association for that identity.
If you need to change or update your server key token provided by Firebase (under Project Settings → Cloud Messaging → Server key) you can do so by selecting the Push Credential in the console and adding your new Server key in the text box provided on the Push Credential page shown below:
We do not recommend that you delete a Push Credential unless the application that it was created for is no longer being used.
When a Push Credential is deleted any associated registrations made with this Push Credential will be deleted. Future attempts to reach an identity that was registered using the Push Credential SID of this deleted push credential will fail.
If you are certain you want to delete a Push Credential you can click on Delete this Credential on the console page of the selected Push Credential.
Please ensure that after deleting the Push Credential you remove or replace the Push Credential SID when generating new access tokens.