Why am I seeing a "RegisterForPushNotifications: token is empty" error after updating the SDK?

This message means your app called a Pushwoosh registration method with a null or empty push token, so the SDK refused to act on it.

Where it comes from

The message is emitted by the Android SDK when registerExistingToken() is called with an empty value. The SDK logs Token is empty, ignoring method call at error level and returns immediately — the call is silently dropped. Note that:

• No completion callback is invoked for this case, so a callback-based integration will simply never fire. Watch the device log rather than waiting on the callback.
• Nothing is sent to Pushwoosh, so the device is not registered and will not receive pushes.

This only affects registerExistingToken(), the method used when your app obtains the FCM/APNs token itself and hands it to Pushwoosh. The normal registerForPushNotifications() flow requests the token from the push service on its own and is not affected.

How to fix it

1. Call registerExistingToken() only from inside the callback that delivers the token (for example FirebaseMessaging getToken() success, onNewToken(), or didRegisterForRemoteNotificationsWithDeviceToken on iOS) — never at app start.
2. Guard the call with a null/empty check of your own so the SDK is not invoked with a missing value.
3. If you do not need to manage the token yourself, drop registerExistingToken() and use Pushwoosh.getInstance().registerForPushNotifications(callback) instead; that path reports success and failure through its callback.
4. If the push service itself never returns a token, the problem is upstream — check that your Firebase / APNs configuration matches the project configured in Pushwoosh.