Activity visible in activity widget but NOT in calendar

So usually when I sync a run, it shows up both in my activities widget and on the calendar widget. Below is an example. On the left side is the calendar widget, and on the right a list of activities. Yellow entries on the left widget are custom workouts, blue are runs and purple are swims. In this case, they match the activities list perfectly.



Yesterday, I bought a Forerunner 15 as a gift for someone. Today, they went for their first run and synced to Garmin Connect. In their case, however, the activity shows in the activity list but not in the calendar. In this case, the yellow entries again represent custom workouts, but there is no blue entry for the run logged today on the right.


The activity does not show up in the calendar and total distance there is seen as 0.00km. Help?