Was this treadmill workout tracked directly with your Garmin device, or was it imported into Garmin Connect from another app or device?

Unfortunately, Garmin only shares workouts that are recorded directly with a Garmin device – not activities imported from third party sources – due to their data sharing policies.

If this was tracked by Garmin, do you mind sending us some logs to investigate? To do this, just navigate to the Profile tab, scroll down to the bottom, and tap 3x quickly on "Version." This will reveal a "send logs" button.