Does Nomorobo Max need to be open in the background? Follow Nope! Nomorobo Max does not need to be open in the background in order to work properly. Related articles How does Nomorobo Max Call Screening work? Where did my Voicemail go? Call Screening Troubleshooting Why do I need to send unknown calls to Nomorobo Max? Nomorobo extension is not appearing in settings