As has been mentioned numerous times on these forums, iCloud syncing via Apple’s servers – especially CloudKit – has not been reliable for many people in the past year.
Why are you trying to use CloudKit? Regarding syncing, the first question you need to ask yourself is, “Do I need a remote sync option?”. Consider these questions…
- Do you need to sync between machines – especially desktop Macs – in different geographic locations?
- Do you have a colleague, assistant, significant other, etc. that needs frequent updates to synced data?
- Are you using a shallow sync, i.e., Download Files: On demand in DEVONthink To Go?
If the answer is no to any of these questions, a local sync on your network is suggested.
There is a forum post on syncing: Sync Types Explained. This is a good place to start.
There is also one specifically about Bonjour: Bonjour Simplified