If your on the current app version i believe your issue might be related to this thread https://community.fitbit.com/t5/iOS-App/Exercises-recorded-in-a-different-time-and-not-showing-data/... in which case there currently isn't a fix.
The problem though is that Fitbit doesn't provide updates about what the "bug fixes and stability improvements" are. It's going to be hard for @LizzyFitbit and @KateFitbit to communicate the fix to the community in a timely manner if at all since they are just as much in the dark as we are.
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