https://forums.garmin.com//showthread.php?t=21208
My data is normally uploaded to Garmin Connect automatically but none of my sessions from today or from yesterday appears on Garmin Connect? What to do?
Your data might have been transferred from your device to your computer but not forwarded on to Garmin Connect since Garmin Connect was unavailable at that time.
Try using the "Upload Selected" option in the Garmin Connect Upload screen.
If your missing activities are listed, check the boxes for them, and then click on Upload Activites to pass them on to Garmin Connect manually.