Try starting the game in location 2. Sometimes Steam doesn't start uploading immediately after exiting the game, and it might take starting it again to trigger the upload.
Either way, you can check in the load window if recent saves are marked as having been backed up to the cloud.
Check the game at location 1 to make sure cloud support wasn't disabled. You can check the globally setting (in the client click on the Steam menu and select Settings, and then Cloud) as well as for the game itself (in the library right click Divinity: Original Sin Enhanced Edition and select Properties, then switch to the Updates tab and check the Steam Cloud section).
Any other guesses? I was syncing between my laptop and my desktop with no problem for weeks. Then suddenly, my laptop shows all the most recent files, while my desktop shows "not backed up to cloud" icon for the last 10 or so saves, and no recent cloud saves. It's not seeing the files that have been saved to the cloud by the laptop. Since the desktop has a bunch of "not backed up to the cloud" icons, I'm assuming it's the problem.
I tried all of the steps you suggested, everything is set to sync everywhere, and both games claim to be synced and up to date.
