Today I encountered a problem in which none of my files on iCloud could be opened. The issue (almost certainly self-inflicted after I’d been poking around in iCloud’s underbelly…) was peculiar in a couple of ways.
Although all files refused to open, Quick Look had no problem displaying every file’s contents (shame that we lost the ability to cut and paste from Quick Look in El Capitan, as that would have presented me with an option for recovery). Another oddity was that iCloud files that were currently open could still be saved to, but once closed, refused to open, showing the dialog above. Yet more worrying was that neither copying and pasting a file to another location outside of iCloud with the Finder nor trying to restore from Time Machine worked.
Logging out and logging back in again also did not resolve the problem, as I’d hoped. However, I was prevented from just trying a full restart as I had critical processes running elsewhere on the computer.
One option that I successfully employed was to use the ditto tool on the command line to copy a Pages document to another location (note that the Pages format is actually a directory rather than a single file, so ditto is a good tool for this). However, while this might be useful in an emergency, it’s hardly a practical solution to repairing the whole of the iCloud Drive.
Instead, I took the seemingly scary option of unlinking the mac from iCloud Drive in System Preferences > iCloud. You’ll get a warning like this:
I then re-enabled iCloud in the hope that this would refresh whatever it was that had become out-of-sorts. Unfortunately, that still didn’t work. I next tried unlinking again, logging out and re-linking after logging in. Still no dice, and by this time I was sufficiently worried that there was nothing for it but to halt all my other activities on the computer and try a restart. Possibly the system holds something in a memory cache that needs to be flushed, I’m not sure. In any case, I took the step of unlinking iCloud first, then restarting, then re-linking after reboot. Success (and relief)!
I don’t fancy trying to reproduce the issue to see if the reboot alone would have solved it, but that would be my first step if the issue occurs again. Otherwise, the unlink, reboot, and re-link method seems to do the trick.