Have you tried restarting your phone and also the Ionic (Press and hold the left button and bottom right button together for 15 secs)? Also long press the left button on your Ionic, then swipe from the right side of the screen to the left, confirm that the setting for notifications is set to on.
If that doesn't work you could try uninstalling the fitbit app from your phone and reinstall it. You may need to go back into settings to re-enable notifications.