Vivofit jr. 2 syncs but no activiyu data is transferred

Got my son a Vívofit Jr 2. Initially the sync process went fine, showing the detailed activity and sleep for each day.
Since last week when it syncs to my Garmin app on iOS the process seems to go ahead normally but only steps are shown with no information at all on the activity and sleep screens.

Any tips on how to fix this?

thanks

Gabriel