My Garmin Forerunner 45 is not recording activities in calendar. After sync, I cannot see al days registered and just can see the last one. My calendar is with lots of empty days. How can I solve it?
Uploaded data is always kept in your account.
Make sure you are using the same account as before. It is VERY common that users accidentally create new accounts.
Login to Garmin Connect Web to see all your data.
Sync with Garmin Express on a computer to upload data when you can't do it through the app so everything is saved in your account.