Recent iCloud photos show exclamation mark when double-clicked
I use iCloud Photo Library to sync photos from my iPhone 7 to my iMac. Everything had been working fine until recently. Now, any photos I've taken on my phone in the past month or so appear in the Photos app on my iMac, but when I double-click on the thumbnails I get an exclamation mark.
Here's what I've tried so far:
- Checked icloud.com, and the full pictures are there
- On the iMac, turned iCloud Photo Library off and then on again. This re-downloaded the entire library, and the recent photos still had the same problem.
- Created a new photos library, made it the system library, and turned iCloud Photo Library on. Same result: the library was re-downloaded, but the recent photos still had the same problem.
Any troubleshooting suggestions? Thanks!
iMac