Posted elsewhere:
Garmin connect has been having issues all day. The site was down for a while, and no one can sync (any garmin device) right now. I'm sure Garmin is working on it. LOTS of people just got new devices over the holidays, which adds to the load, and many new users want to sync pretty often. Once people get used to things, the "sync requests" will slow down, and things will get more stable. (The Garmin Trackers hold about 30 days of data, so even if you go a few days without syncing, it's not a big deal)
As a side note, Polar Flow (the GC equivalent for Polar Devices) and Misfit (the Misfit Shine and Flash) seem to be having similar issues today. Everyone is experimenting with their new trackers before they go back to work on Monday!