This Google Help page lists what you get with and without various subscriptions for each camera and doorbell. Note that with new cameras and doorbells you get a free 30-day Nest Aware trial subscription.
I apologize for my late response, and thank you for all of your patience while waiting for a reply. I am wondering if you were on a Nest Aware trial that may have ended. Here is a great link on how Nest Aware works and how to subscribe. In addition, here is a link on how to manage your subscription. Thanks for your help here, MplsCustomer.