If you tap on all activities, do you see anything? Or tap on your profile icon to view all activities. Can you send a screenshot of what you're seeing or not seeing?
When you do your strength or cardio workouts are you starting, stopping, then saving? Can you view those activities in the watch history?
You can also sync using Garmin Express or do a manual upload directly from the watch. That would also tell us if something is wrong with the workout (corrupt file) or there is something wrong with the Garmin Connect app and/or how it is syncing with your watch.
