My 310xt is stuck in a loop where it tries to sync, fails, and tries again. The error is, "Sorry, we couldn't sync your device. Please try again." No additional details are given. For some reason, it thinks there are two activities to sync, one from today and one from Dec 30, 1989. I have tried removing the device from Garmin Express and re-adding it but that didn't help, same error.
The file from 1989 is a file what would contain data from a TANITA Health scale if used. Garmin Express should ignore that data now if no scale is used. Make sure Express is up to date, see FAQ: How do I update Garmin Express?.
When was the last time you successfully uploaded an activity to Garmin Connect through Garmin Express? Do you use the 310XT outside with any other sensors such as a heart rate monitor? Have you recently modified the Heart Rate Zones in Garmin Connect?
I got the same error today with my 800. I have been syncing with no problem up until now. Only thing different is I added a second 800 to my account yesterday and synced that one last night. It is the original 800 that gives the error. File uploaded without issue to Strava using the Communicator plug in. I'm on a mac.
I'm having the same problem with my 210. It syncs fine to the old Garmin Connect website (I'm not loving the fact that the new Garmin Connect requires me to use Garmin Express, since it won't work) and to Dailymile. It even managed somehow to install the latest firmware. But it won't sync activities ever. Whenever I plug it in, I get the same error in Garmin Express. I've already tried deleting and re-adding the device. I'm running the latest version of Garmin Express on Mac OS 10.9.3.
had the same problem with ForeRunner 210. The error was happening because of one .fit file that seems to have been corrupted. Once I manually deleted the .fit file of my device (located under /Volumes/GARMIN/Garmin/Activities on Mac) the Garmin Express was able to sync successfully with no errors.
