I getting this error everytime i tried so sync my Garmin310XT with Garmin Express. I have takeing a new Mac with the latest Garmin Express v. 6.6.0.0 installed. The error is writed in danish, the english info is "An error occurred while synchronizing Garmin Connect" see picture.
Some times is also starts sync an then after a while the watch is turned off even when there still a lot of battery on the watch ciq.forums.garmin.com/.../1383407.png