Could you go to https://connect.garmin.com/modern/report/-1/all/last_four_weeks, click on the link "Activity List", and verify whether the Tacx activity is really not there? My Tacx activities are listed there without any issues. Also double-check that you use the very same account for the Tacx Training app and for Garmin Connect.
Also my HRV status looks v different to yours.
If I go to my training load you can see the activities listed in the my activities posted earlier simply aren’t there