Great idea – glad you’re looking for solutions to answer the door more quickly!
However, on my Andriod, Rapid Ring 1.0.17 installed just now, the main app page says “Alerts Disabled” under the entry for the Doorbell (Pro).
In the settings page, the circle around the bell icon is blue, indicating that’s on.
When I press the white running man icon to turn on the Motion alerts, there is the big green check mark “Saved” dialog, the icon goes blue for a second, and there is a banner saying “Motion Alerts have been enabled”… but then it reverts to the white (disabled) state.
Back to the main screen, and it says “Alerts Disabled”.
The cause was that Motion Alerts were disabled in the larger Ring app, also installed on the phone. The settings are inter-related, but cause confusion since Rapid Ring doesn’t seem to be able to make the change stick…