If your library isn’t matching across iPhone, iPad, and Mac (books missing on one device, a status not updating, recent changes not appearing) almost every case can be fixed with the right procedure. This guide takes you from the quickest checks to the full multi-device recovery.
The most important thing before anything else:
⚠️ On the device that has your complete, up-to-date library, create a manual backup right now.
Open Book Tracker → Settings → Backup & Restore → Create Backup.
The procedures below are safe only if you’ve done this. Don’t skip it.
🆘 Quick fix: try these first
Most sync problems are solved within 60 seconds by checking three things:
- All devices are signed into the same Apple ID.
- Book Tracker is enabled for iCloud on every device (path below in Step 0).
- Wi-Fi is on and stable. iCloud doesn’t sync well over a weak network.
If everything looks right but the library is still out of sync, leave Book Tracker open in the foreground on each device for 2–3 minutes. iCloud sometimes just needs time to catch up.
If that doesn’t help, the rest of this article walks you through everything.
The Sync Status screen: your dashboard
Before doing anything else, open Book Tracker on every device and go to the iCloud Sync section in Settings → iCloud Sync. This screen is your dashboard: it tells you exactly what each device is doing right now.
You’ll see three rows:
- Setup — the initial handshake between Book Tracker and iCloud.
- Read — downloading changes from iCloud to this device.
- Write — uploading changes from this device to iCloud.
Each row can be one of three colors:
- 🟢 Green — that step is healthy. Sync is working.
- ⚪ Grey — that step is in progress. Just wait; nothing is broken.
- 🔴 Red — there’s a problem. The row tells you which one.
A device is healthy when all three rows are green. If a device shows grey, it’s working and you should give it a few minutes. If a device shows red, that’s the device you need to look at and the red label tells you what the problem is.
Knowing this changes everything: instead of running a reset blindly, you fix only the devices that actually need fixing, and you leave the healthy ones alone. The rest of this article is built around that idea.
iCloud Drive vs iCloud sync: a key distinction
Before troubleshooting, it helps to know that two different features both use the word “iCloud”:
- iCloud sync (what this article is about) — the real-time mirroring of your library across devices. Enabled in System Settings, not in Book Tracker.
- iCloud Drive backups — backup files Book Tracker can save to your iCloud Drive folder. Enabled in Book Tracker → Settings → Backup & Restore.
If your backups aren’t appearing on another device, that’s an iCloud Drive backup destination issue, not a sync issue. See the backup tutorial instead.
If your library content (books, reading statuses, notes, …) isn’t matching, you’re in the right place. Continue.
Errors that only require patience (don’t reset!)
Some red errors on the Sync Status screen are not real failures. They are the system telling Book Tracker to slow down, and they will go away on their own. Don’t reset, don’t reinstall, don’t take any action. Just wait, and check the Sync Status again in a few hours.
These are the known “just wait” errors:
CKErrorDomain 6 (“Service Unavailable”)
iCloud has temporarily stopped accepting uploads from your device. This is called throttling and it’s a protection that Apple’s servers apply when an app tries to push a lot of data at once, most often after a big import or after restoring a backup. iCloud lifts the limit automatically after some hours; sync resumes by itself.
CKErrorDomain 7 (“Request Rate Limited”)
Too many sync requests in a short time. Same idea as error 6, with a slightly different threshold. Same answer: wait, don’t reset.
Cocoa Error 134419
This is an internal Core Data error meaning the system has deferred (paused) Book Tracker’s sync because it was using too many resources. It appears most often after importing or restoring a large library.
The data is not lost. iCloud will retry automatically when the system has resources available.
What to do for any of these three errors
- Don’t reset and don’t reinstall Book Tracker. That can make things worse.
- Close Book Tracker and check the Sync Status screen again in a few hours.
- Keep the device on Wi-Fi (not Low Power Mode) so the system can retry in the background.
- If you imported or restored a very large library, give it at least 6–12 hours before worrying.
Most of the time, by the time you check back, the Sync Status will be all green and you’ll have done nothing.
Diagnosing your situation: which devices need fixing?
Open Book Tracker on every device, go to Settings → iCloud Sync, and look at the three rows on each. Then check the chart below:
| What you see | What it means | What to do |
|---|---|---|
| All devices show all green ✅ | Sync is working everywhere. | Nothing. You’re done. |
| One device has grey rows | That step is in progress. | Wait a few minutes, then re-check. |
| One or more devices show red, but the error is CKErrorDomain 6, CKErrorDomain 7, or Cocoa Error 134419 | The system is throttling. Not a real failure. | Wait several hours; don’t reset. |
| One or more devices show red with a different error message, while at least one other device is all green | Some devices have a real sync problem; others are healthy. | Do the reset procedure below, but only on the red devices. Don’t touch the green ones. |
| All devices show red with non-recognized errors | A wider problem. | Follow the reset procedure starting from the device with your most up-to-date library. |
🚫 Important rule: never run the reset procedure on a device that already shows all-green Sync Status. You risk forcing the healthy device to re-download everything from iCloud, slowing things down and potentially overwriting recent changes.
Step 0 — Make sure iCloud is enabled for Book Tracker
Before resetting anything, double-check that iCloud is actually enabled for Book Tracker on every device:
- iPhone / iPad: Settings → Apple ID → iCloud → Show All → Book Tracker must be ON.
- Mac: System Settings → Apple ID → iCloud → iCloud Drive → Options → Book Tracker must be checked.
If iCloud is disabled on any device, that device cannot sync. Enable it and wait a few minutes; in most cases, that alone fixes the problem.
Step 1 — Reset on a device that’s out of sync (red Read or Write)
⚠️ Apply this only to devices that show a non-recognized red error in Read or Write in the Sync Status screen. Do not apply it to devices that are all green or that show one of the “just wait” errors above.
The reset re-builds the connection between Book Tracker on this device and iCloud:
- On the out-of-sync device, open Settings → Apple ID → iCloud → Show All.
- Find Book Tracker and turn it OFF.
- Open Book Tracker. Its library will clear locally. This is expected. (Your data is safe in iCloud and you’ve already taken a backup of any device that has the complete library.)
- Go back to Settings → iCloud → Show All and turn Book Tracker back ON.
- Open Book Tracker and wait while it downloads the library from iCloud.
- Re-check the Sync Status screen on this device. If everything is green, you’re done.
If you have more than one device showing a non-recognized red error, repeat Step 1 on each of them (one at a time, waiting for each to finish before moving on).
Step 2 — Reset on the main device (only if Step 1 wasn’t enough)
If you ran Step 1 and the affected device still can’t pull recent changes, the upload from your main device (the one with the complete library) is probably stuck. You’ll repeat the same toggle, but on the main device.
⚠️ Reminder: you should already have a manual backup of this device from the very top of this article. If you don’t, stop now and create one before continuing.
- On the main device (the one with the complete library), go to Settings → Apple ID → iCloud → Show All.
- Turn Book Tracker OFF.
- Open Book Tracker. The local library will clear — this is expected.
- Turn Book Tracker back ON.
- Open Book Tracker and wait. The app will reconnect and start re-uploading your library to iCloud.
- Watch the Sync Status screen on this device. When Setup, Read, and Write are all green, the upload is complete.
Step 3 — Restore the manual backup safely (multi-device procedure)
After Step 2 the main device’s library might temporarily look incomplete: some recent changes may not have made it to iCloud before the reset, so the version downloaded back is older than what you had locally. This is exactly why you took the manual backup at the start.
Restoring is straightforward, but because iCloud will propagate the restore to all your other devices, a small multi-device dance is needed to avoid surprises:
3.1 — Before restoring, close Book Tracker on every other device
On every iPhone, iPad, and Mac other than the one where you’ll restore, fully close Book Tracker. (On iPhone/iPad, swipe up from the bottom and flick Book Tracker off the App Switcher. On Mac, choose Quit Book Tracker from the menu.)
This way they won’t try to read from iCloud while the main device is still uploading the restored library, which would otherwise show them an inconsistent half-state.
3.2 — Restore the backup on the main device
- On the main device, open Book Tracker → Settings → Backup & Restore.
- Select the backup you created at the very beginning of this procedure.
- Tap (or click) Restore and confirm.
- Open the Sync Status screen on this device.
3.3 — Wait for the sync to complete
Keep Book Tracker open in the foreground on the main device, with the Sync Status screen visible. Setup will turn green first, then Read, then Write. That order means iCloud has accepted everything and the upload is finished.
This step can take a while, especially for large libraries. Several minutes is normal; with thousands of books, it may take much longer.
During the upload it is completely normal to see one of the “just wait” red errors appear on the Sync Status screen:
- CKErrorDomain 6, CKErrorDomain 7, or Cocoa Error 134419.
These mean iCloud is throttling because the upload is large. Don’t reset. What to do:
- Close Book Tracker.
- Wait a few hours (longer for very large libraries, overnight is safe).
- Reopen Book Tracker and check the Sync Status. Usually you’ll find all-green by this point.
- If you still see one of those three “wait” errors, close again and try again later. iCloud will eventually resume.
Repeat as needed until Setup, Read, and Write are all green on the main device.
3.4 — Bring the other devices back, one at a time
When the main device shows all green:
- Open Book Tracker on one other device — just one.
- Go to that device’s Sync Status screen and watch.
- Setup will turn green first, then Read will work through what’s new, then Write will catch up.
- Wait for all three rows to be green on this device before moving on.
- Once this device is fully green, repeat on the next device. Again, one at a time.
Bringing devices back one at a time prevents them from competing for iCloud bandwidth at the same time, which is what otherwise triggers the throttling errors all over again.
When every device shows all-green Sync Status, your library is fully restored and consistent everywhere. You’re done.
Tips for syncing large libraries
Libraries with hundreds or thousands of books need a little more patience than smaller ones.
- Give iCloud time after big imports. If you just imported a library from Goodreads or another app, leave Book Tracker open and connected to Wi-Fi for several minutes. Possibly longer for very large imports.
- Open the app on every device. After a big change on one device, opening Book Tracker on the others triggers them to check iCloud for updates.
- Avoid force-closing the app during a long upload. Background uploads continue silently; force-quitting can pause them. (The Step 3.3 procedure above explicitly closes the app. That’s different: it’s after throttling appears.)
- Keep devices on Wi-Fi during heavy sync. Cellular sync works but is slower and more interruptible.
- Update to the latest iOS / iPadOS / macOS. CloudKit reliability improves with each Apple update.
- Manual backups are your friend. Before a large import or bulk edit, create a manual backup. Both as a safety net and as a faster way to bring a new device online (a restore is often quicker than waiting for iCloud sync from scratch).
Extra tips
- Keep Book Tracker in the foreground and connected to Wi-Fi until syncing completes.
- Disable Low Power Mode on iPhone/iPad. It can pause background data transfers.
- After enabling sync on a new device, the first sync downloads the entire library; on large libraries this can take several minutes.
- If you regularly switch between two Apple IDs (e.g. personal and work), each Apple ID has its own separate library in Book Tracker.
- The Sync Status screen is the truth. If it says all green, sync is working, even if you don’t yet see a change you made elsewhere. Give it a couple of minutes.
What to do if nothing above worked
If you’ve followed everything above and your library is still wrong:
- Take a fresh manual backup on the device with the most up-to-date library.
- Wait a few hours (iCloud sometimes resolves issues on its own).
- If still broken, contact us at support with:
- which device is out of sync;
- which error appears on its Sync Status screen (Setup / Read / Write, and the exact error label);
- whether you’ve already restored a backup;
- the size of your library (approximate book count).
We’ll help diagnose further.
👉 Apple’s general iCloud troubleshooting: If iCloud isn’t working.