@AOttney Welcome to the community forums.
Thanks for the details shared in your post. Most Fitbit devices automatically recognize and record high-movement activities through the SmartTrack feature. To start, your device recognizes activities at least 15 minutes long. If your Charge 4 isn't registering your Bike activity, I'd recommend lowering the auto-exercise recognition setting to 10 minutes. You can do so on the Fitbit app:
On the Fitbit app dashboard, tap the Exercise tile.
Tap on the gear icon at the upper right corner.
Tap an exercise, and adjust the duration or turn off Auto-rec. Make sure to tap on "Save"
If that doesn't work, I suggest you to restart your Charge 4 following the tips here. Also, I'd advice to use track your activities using the connected GPS option too, you can track specific exercises such as a run, bike, swim, or yoga with the Exercise app. To see real-time stats, capture GPS data and review a post-workout summary on your wrist. For more information, including how to customize the exercise types on your device, see How do I track my workouts with my Fitbit device?
For your missing activity, you can manually log it on the Fitbit app.
Hope this helps!
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