Activities missing in Garmin Connect

this is happening to mine, anyone know answer at  garmin?

I would make sure that you're using the same account on the Garmin Connect web and the Garmin Connect app. Note any error messages when syncing your device. If anyone has any screenshots or error messages they could post, that might help. Otherwise, contacting Garmin support via phone, chat, or email would be the next best option.

Same happening with my wife's brand new vivosport. Worked fine for a few weeks, now 3 out of the last 4 activities simply don't sync to connect app. Did a test activity without GPS and it synced, but the other 3 don't. Will try again without GPS to see if this is the common denominator. 

All other vitals seem to carry across (Steps, HR, sleep time, etc) so the connection between the phone and watch is good, it's rather that the activity files are corrupt and not saving to the watch correctly. This is a major issue and will be returning the device if not resolved (or at least acknowledged) by Garmin ASAP. 

I tried with and without GPS, both randomly dont sync as activity. The activity is saved on watch, i can see it stored in File, but it wont sync to phone and wont upload when i sync to garmin express on PC. The annoying thing is on express it shows the raised heart rate but isnt marked as an activity, I get financial rewards from my medical insurer but they only reward on an activity, so i either re-do activity again or lose the financial rewards that week, so its costing me money. I called Garmin, they have never heard of this fault (try reading forum), so they dont know how to resolve except suggesting forgetting watch in phone and re-connecting it all again every time i do activity. The re-setting works, but thats not really a practical solution

Same, i've tried multiple combinations of with/without GPS, different type of activies, saving/discarding but no apparent repeatable cause. Syncing with Garmin Express also doesn't help. As with your problem the activity shows on the watch summaries (times, distance, etc) but the detail (route etc) never gets synced to the connect app of affected activities. My current suspicion is that their might be damaged storage on the watch as I can see in the event logs the CHKDSK run seems to be throwing errors occasionally. I'll be running a chkdsk myself this evening (when my wife is home with the watch) to confirm. This would explain the seeming sporadic nature of the problem.

The lack of Garmin engagement or support on this forum is shocking.

be interested in your result of chkdsk