I have just encountered a similar problem today with my Forerunner 10. It Synchs in Garmin Express, but doesn't show up in my activity history on Garmin Connect. When I have tried to manually import the .fit file I get a message saying that activity has already been added, and I can then click on it and see the activity on Garmin Connect, but when I return to my dashboard or the activity history it is still not there. My Garmin Connect account is also linked to Endomondo - and the activity appears there, so it has obviously synched across to there - I just can't see it on Garmin Connect - frustrating! This is the first time to encounter a problem like this - but it appears to be a problem with the Garmin Connect website rather than the device synching.
