How to fetch FCM registration token

Question

I am using the below-mentioned code to fetch the FCM registration token, but when I reinstall the app the token doesn't generate and giving the error java.util.concurrent.ExecutionException: java.io.IOException: SERVICE_NOT_AVAILABLE

Please help.

FirebaseMessaging.getInstance().getToken()
                .addOnCompleteListener(new OnCompleteListener<String>() {
                    @Override
                    public void onComplete(@NonNull Task<String> task) {
                        if (!task.isSuccessful()) {
                            Log.w("TAG", "Fetching FCM token failed", task.getException());
                            return;
                        }
                        fcmToken = task.getResult();
                    }
                });