Voice Notification - Could not find compatible locale for language code 'en_US'

Hello! I am trying to get voice notifications via VoIP. I am using VoIP.ms service and it says it is successfully registered. When I toggle on an alarm, the log gives an error of: Could not execute notification job NotificationJob[id=NJob_6, users=1, events=1], the delivery media system was not available. Details: Could not find compatible locale for language code 'en_US'. I've tried other English language settings on my user. Attached are screenshots of our setup. We installed Katherine voice notification and have an active license. Any idea why I am getting this error?