Ok, I know people have been asking about the situation with Modern Connect and I am having issues uploading also. Whenever I try to connect I get express advising its trying to download from Garmin Connect 6 items (Activities) but there is nothing to download? I tend to spend more time trying to upload my activity to Garmin Connect than I actually do for the activity! Does anybody have any idea what the issue would be and/or when we can expect something to work?
Well for many it does work, why it's not working for you is difficult to say given the limited info you've provided.
Did everything work with Connect Classic? What happens if you switch back to Classic? Does it then work? Which OS are you using? What device are you using?
SUSSAMB is right. It's true for a lot of devices, including my Edge 705 and 800, my Fenix, my VIRB Elite, and even my nuvi 755T. Manual upload is still available: http://connect.garmin.com/modern/activities, click on "Import". The devices that don't use ANT Agent mount as disks and you can read activity files right off them. You could do that with the Old Garmin Connect as well; the Upload button was everywhere, and you didn't have to use the Communicator Plugin. I never used it on the old GC, it was always too slow compared to manual uploads right off the device.