CoreData CloudKit Sync not working between iPad and iPhone

I have an application that uses CoreData as a persistent storage and recently implemented the support for iCloud-Sync. All works fine with my test devices (iPhones) and for most my users the synchronisation works as intended.

However I have been getting a few emails lately, notifying me that the iCloud synchronisation does not seem to work for some users. All of those users are using iPhone devices and are trying to sync the data of the app to an iPad (or the other way around). It also only seems to be working one-sided. Data which is created on the users iPad syncs to their iPhones fine, however the iPhones data does not sync to their iPad.

I think this is a weird issue and I haven't been able to resolve it yet. My app is designed for iPhone (iOS) only so far, so the iPad users are using the iPhone version on their iPad.

What could cause this issue and how can it be resolved? Would be really grateful for some guidance!

is "iCloud Drive" enabled?

@deeje Are you asking if the users enabled it on their iCloud account? If so, I'm guessing yes but I don't know for sure. The app itself uses iCloud Drive to save documents that can then be viewed between all devices, so yes the app has iCloud Drive enabled.

Also seeing this issue. If anyone knows how this can be resolved, we'd appreciate that!

I was guessing that the issue may be caused by me not having an explicit iPad version of the app. I now have an iPad version of the app but the issue still exists according to my users, it is working fine on my test devices however. Can anybody tell me if it may be an issue with development vs production iCloud containers? I have pushed the schema to production already but the issue persists...

Any resolution to this @benedom. I've just released an iPhone app and have the exact same sync issue to iPad. iPhone app works fine and receives sync from iPad. iPad and Mac (Catalyst) apps only sync with each other, don't receive anything from iPhone.

Hey, can you help me troubleshoot this issue? My app is functioning correctly with the development build, but when tested on TestFlight (production build), iCloud sync functionality is not working.

Having the same problem. I enter data on my MacBook Pro and I see records updated on the CloudKit console. My iPhone app sees the updates, no problem. But my iMac doesn’t.

Conversely, records updated on my iMac remain in local storage.

CoreData CloudKit Sync not working between iPad and iPhone
 
 
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