On the new version of Garmin Connect? or the old version of Garmin Connect?
You need to have Garmin Express installed to use the new version, or you can look for the "import" feature and use it to upload your activities without having to install Garmin Express. I don't use the new version so I'm limited in what I can tell you about it.
On the old version of Garmin Connect, you still need Garmin Communicator (AFAIK) or you can do a "manual upload".
It would also be a big help to know what device you use. If it requires an ant stick, then the above info isn't everything you need to know.
There is no more upload button. Garmin Express must be installed on your computer. It is supposed to automatically upload your rides when the device is connected.
It might be that you need an updated version of Garmin Express. It might be you or someone inadvertently changed a setting in Garmin Express so that it doesn't upload automatically or does not even start running at boot.
If none of the other users here get you going, then you need to call or email Garmin Support.
NOTE: This is only for users of the modern or new Garmin Connect.
I am not able to upload my rides from my Forerunner 10. I installed the Express version, and it still says no device connected when I try to upload. It was working perfectly 2 days ago. I upgraded my computer also in hopes that would fix the problem.
