I’m not sure about the others in this thread, but for myself and MANY other people, Photo Stream has been flaky for a couple of YEARS before this particular issue even popped up. Even when it was “working” it was only half working. It had to constantly be switched off and back on on both the iDevice and the Mac it was uploading to and sometimes even a sign out and back in of the AppleID.
I just used this latest issue as the final reason to just connect my iPhone to my Mac once in a while and import ALL my pictures AND VIDEOS all at once, all in their native format and high resolution. Faster, easier, and more reliable and complete.
I know my way won’t be better for everyone - when Photo Stream works it can be a really sweet transfer/sync method - but Apple is basically letting it deteriorate, and I personally am tired of dealing with it.