Odd iCloud syncing issue
This is genuinely because of multiple iCloud accounts used on one PC. Just for the sake of experiment, try installing iCloud on a PC where no other iCloud have ever been installed. I am sure, it will sync with it, and it is certainly a cache problem. 

Secondly, regarding the My Photo Stream not showing up anything but you can still see 3 photos when you click open folder ... this is because Photo Stream shows photos when its a collection or multiple of 5 photos (e.g 5, 10, 15, 20), so if you have 5 photos in the folder, it will show up, then it won't show until it get 10 (in case of total photos &lt;> multiple of 5, it will come up with all photos it has, as the last photo will tell that this is the end of the album). Make sure it is not a network drive, as iCloud doesn't re-download photos once it is interrupted.