Hello @Enjh and welcome to the Help forum. I get FaceTime and many other app notifications on my Versa 3. Is your Sense brand new? Remember, you need to receive a notification once before you can toggle it to On in your App Notifications.
This happens every time you put a new device on your account -- those app settings are device specific. You also wipe that slate clean if you do a factory reset on your device.
Laurie | Maryland
Sense 2, Luxe, Aria 2 | iOS | Mac OS
Take a look at the Fitbit help site for further assistance and information.