Workouts and calories burnt not showing on activity summary on iPhone

I am new to Apple Fitness+, so I hope this isn't too dumb a question. I don't have an Apple Watch. That said, a week ago I started workouts with Fitness+ on iPad - mostly rowing and yoga. Now on some days, the activity summary on iPhone will show my calories burnt perfectly fine, and below I can also see the training units I've completed. On other days, however, the trainings are missing and also the calories aren't included in the summary. What am I missing here?