Photo Stream, without exception, has a lot of problems like: One of the first things you'll notice on FAQs on Apple (for Photo Stream) is this rule: you'll need to have more than 20% battery for Photo Stream to work. Make sure there's enough battery and a good, solid Wi-fi network (or LTE, but Wi-fi is preferred always).2.
Read-only Permissions Did you change the default folder for Photo Stream in Windows (via i Cloud Control Panel)? If you changed the folder to someplace else, do this: Read-only permissions can be a pain in the back especially in Windows.
As for prior notice, this may have been talked about for a while in Mac forums and other such tech media, but I do not necessarily check those as a matter of course, and I don't think I should have to.
It does connect, but it takes ages to load the photos, and it stops after a certain point, i.e. Therefore, I have kept My Photo Stream activated, in the hope of downloading photos from it as I was doing before. I don't think it is an internet connection issue either. There is some buggy behavior with Photostream, that's for sure.
Unfortunately, the Photos app simply isn't working properly with My Photo Stream. I have to keep toggling it off and back on to make it work, and even then it's a bit sluggish.
Your image says it's still uploading and I think that needs to complete first. I have the same issue with photos going from i Phone and i Pad to i Cloud immediately, but not going to my i Mac.
I turned off Photo Library on my i Mac which prompted another 19000 photo upload which seems to be stuck at 28.32GB of some 76GB.