I encountered the same problem again - Garmin Express error syncing.
I successfully sent last night's activity (which is the only one I had after the hard reset) from F3 to Garmin Connect.
When I created a new workout and tried to send to F3, everything incluidng all the preset workouts and activity were washed out. So I used Garmin Connect and tried to send last night's activity to F3 again but an error message at Garmin Express showed "cannot syncing with Garmin Connect".
In my recent post I was told that the file was corrupted....but last night activity was a freash one after the hard reset...how could a fresh activity be corrupted while nothing was done to the watch ?
FYI, I was on software - 6.27 beta.
Please help and thanks in advance.