An error occurred while downloading a larger version of this photo for editing. Please try again later.

I've moved to photos from iphoto and for a while all was good. And quite exciting. My entire 15k photos have migrated and are available on all my devices.

Suddenly, I get this warning when I select or try to edit a photo: Cant Download Photo: An error occurred while downloading a larger version of this photo for editing. Please try again later.

There is an exclamation mark and a warning triangle on the picture. I am only able to test on my ibook as my Imac is out of action.

If I log in to icloud in Safari, I can down load the full sized image no problem. Any one got any ideas?