If you tracked the workout with a third-party app like Strava, Garmin Connect, or Zwift, the source app sometimes takes a few minutes before it writes the workout into Apple Health. Until that happens, MoveFirst has nothing to read, even though the workout already exists in the source app.
The reliable nudge is to open the source app yourself:
- Open the app you used to record the workout (Strava, Garmin Connect, etc.) and wait a few seconds. The workout should appear in its feed.
- Swipe back to the home screen to background it.
- Open MoveFirst. The workout should sync within a few seconds and your earned time should fill in.
Apple Watch and the built-in Workout app write to Apple Health instantly, so this only affects third-party apps. Zwift in particular routes through Strava, which adds an extra hop and an extra possible delay.