I have a 310XT that I've had for a while. I've tried uploading my workouts, but they do not appear on Connect. Express shows that I sync'd without any errors. I've removed Express and reinstalled, I removed my 310XT device from Connect. Tried to sync again, device showed up on Connect, but no data. I tried to resend all data, but had same results.
My GPS64st is new and have never successfully sync'd data to Connect. I can go into Express and it says it sync'd, but like the 310, no data on Connect. Also the device does not show up in Connect.
Also tried sync'ing using the Mobile App. Device connects to phone, but no data on Connect.
I'm using Windows 8.1
Express 4.0.11.0
GPS 64st is 3.7
310XT is 4.5
Also forgot to add: I checked the directories on my PC for the data: C:\ProgramData\Garmin\CoreService\Devices\<ID>\Sync\Download
They were empty.