Sometimes, for entirely inexplicable reasons, the Photos app on your Mac will stop syncing with the photo libraries on your iPhone and/or iPad.

When it works, Apple's simple cross-device photo syncing solution is one of the most elegant implementations of the technology you'll find on any operating system. When it doesn't work, it's a disaster.

The Nuclear Option

If it's ever happened to you, you probably Googled around for some answers and ended up disabling syncing on all your devices, then turning it back on. And it probably worked. Great!

Except, no. This is the nuclear option. Your entire photo library will need to re-download. If you've got thousands of photos, it could take hours, if not days. Use it as a last resort only.

The Smarter Option

There is a better way. It involves tinkering with the Activity Monitor, nothing more. Best of all, instead of re-syncing your whole library, using this method will let Photos resume from wherever it was up to when the glitch occurred.

Follow the steps below to force Photos to start downloading new photos again:

  1. Quit the Photos app (do not just close it).
  2. Open the Activity Monitor (use Launchpad to find it if you're struggling).
  3. Type Photos Agent in the search box.
  4. Click on the Photos Agent entry to highlight it.
  5. Click on the cross icon in the upper left-hand corner of the window.
  6. A new window will pop up. Select Force Quit.
  7. Relaunch the Photos app.

Your photos should now start downloading and syncing once again. You can see whether the fix was successful by looking at the bottom of the Photos window. It will let you know if items are being downloaded.

Did the fix work for you? What problems did you encounter? Let us know in the comments below.