I last had a workout automatically sync'ed to Garmin Connect on 7th March. Since then my workouts on March 8th, 9th, 13th, 14th, 15th and 16th have all failed to update Garmin Connect. However, I know the uploads by Garmin Express using the ANT+ stick are working, because I have also set up Garmin Connect to share the uploaded Garmin data with Strava - and I can see that Strava has not failed to be updated even once over that same period.
I know around the time these problems uploading to Garmin Connect started for me there were some fails being reported in the Garmin Connect Status page (https://connect.garmin.com/en-US/status) - but every time I look at that page more recently after another failure to add data to your website
Thanks
Andy