Photostream often fails on my iMac inasmuch as it fails to download new photos taken on my phone. The fix is to select Preferences in Photos on the Mac and untick MyPhotostream. Close the preferences window and your Photostream album will (rather worryingly!) disappear.
Now Open preferences again, tick MyPhotostream, close preferences and cross your fingers!
Of course, your problem may be different from mine. Good luck.
Hmm tried that- no luck!
I also notice that bookmarks that I have created recently on my ipad have not been copying over to the mac. Could that be a clue?
(I also had look on my web based icloud, but could not find reference to Photostream, safari or bookmarks)
Shame. Apart from the usual 'sign out of iCloud and then sign in again', I can't think of anything else. I have the feeling that Apple would like to ditch MyPhotostream and have everybody use iCloud photos. I don't suppose you've accidentally turned on the latter by any chance?
I have tried the process described above with no luck and I have also worked through Apple's support note (here), also with no luck.
I fear that Trevor is correct and that Apple intends to end Photostream because it states: "If you've recently created your Apple ID, My Photo Stream may not be available". That implies that it is now only available if you've had it before some unstated date. In my case, I recently changed my AppleID because it was using an ancient E-Mail, address that I want to retire; possibly that is enough to remove my "entitlement"?
Apple offers no further explanation, MacWorld suggests 2018 as the cut-off date but also reports older Apple IDs stopping working for unknown reasons. I'm not optimistic of getting it back.
I interpreted the phrase “ if you recently created your Apple ID, my photo stream may not be available “ differently. I feel it means that you may have to wait a few hours after changing your Apple ID for everything to get sorted out (server updates for example)
Hmm, my latest variation on the problem is that my iPhone (2020 SE) doesn’t even bother to put its own photos in its own MyPhotoStream album, let alone upload them. It does though receive photos taken on my iPad so it’s working one way.
Even stranger, Mary’s iPhone started showing the same problem at about the same time but then, a week or so later, hers started working again. 3wks later, the problem still persists on my SE.
The feature does seem to be dying a very untidy death.