iMac Notes not syncing to iCloud

Open the Activity Monitor app, search for "bird" using the search bar top right. Select bird then kill it using the "x" on the toolbar.

If search can't find bird then hit View in the menu bar and select All Processes then search again.

Not a guaranteed fix, but worth a try if iCloud won't synch.

Not from me I'm afraid. All my iCloud-synched apps fail to synch on a regular basis but I can usually fix it by turning iCloud off on one or other of my devices and then turning it on again. It's a pain cos I don't find out that something hasn't gone from Mac to phone until I miss an appointment or can't see my shopping list on reminders.. In my experience iCloud is flaky but given that very few report problems I assume it's something deeper related to Apple ID given that it follows me around, even on devices that have been set up from new, not copied across from previous devices. My problem is in both directions Mac to iPhone and vice versa and slightly different from yours in that I don't get any indication that synching is not happening.

Just a thought - when you turn off iCloud for Notes on your Mac do you select the option to delete all the Notes on your Mac? If not then you should try that. They'll be recreated when you turn it back on again although, as you point out, you'll lose changes that haven't synched from Mac to iCloud.

Finally - I regularly use an app called "Notes Exporter", which does what it says on the tin. I do TM backups but Notes/iCloud is so unreliable that I was concerned about losing them all so I use the app every month to create plain-text backups. Note that iCloud isn't a backup service.

I'm out of ideas except for a daft question, so please don't be offended. You know that only the 269 iCloud Notes will sync, not the 4 Notes that are not in iCloud?