Select your product to confirm this information applies to you
Garmin Connect Activities Only Display Summary Data
Garmin fitness devices record each activity with summary data and a track log. Each point recorded in the track log includes details about your activity (e.g. heart rate, cadence, location, and other relevant data). If your device begins to run out of memory, when creating track logs for newer activities, track logs for older activities will be removed to make room for the new data. Once these track logs are removed they cannot be recovered. You are still able to upload these older activities to your Garmin Connect™ account, but only summary data will be present.
To avoid losing detailed activity data:
Upload your data to Garmin Connect on a more frequent basis.
Refer to your owner’s manual for additional information regarding memory limitations.
Following the above guidelines will prevent summarized activities from appearing within Garmin Connect, and will allow you to see your data displayed within graphs (as well as on the map when applicable).