Run activity not linked to Garmin Coach training plan

Can anyone tell me how to link an activity to a Garmin Coach training plan? I set up a Garmin Coach 5K run training plan earlier today and synced my watch. It prescribed a Benchmark Run as the first workout, so I started a Track Run activity, and it showed that Benchmark Run workout. I selected "Do Workout" and executed the workout as intended. But after I saved the activity and synced my watch again it doesn't show up in the training plan. The same Benchmark Run still shows as today's Garmin Coach workout. The calendar shows both the scheduled workout and the recorded activity, but they're not linked.

connect.garmin.com/.../12629155180