Notes from iCloud account don't sync with devices when added as secondary account

Solution 1:

I have the same problem syncing with my wife's notes. I found an obscure note in a marginally related Apple article about this: https://support.apple.com/en-us/HT205015. At the very end, under "Learn More" it says

"If you’re signed in to more than one iCloud Mail account on your iOS device or Mac and have notes syncing turned on, you can only use the new Notes features with your primary iCloud account. You can see your primary account in Settings > iCloud, or System Preferences > iCloud."

This really sucks since there is no workaround once you've upgraded.

Solution 2:

Yes indeed. Although in some ways it's worse than that. If you have 3 accounts in (say) a family, then "Mum" "Dad" and "Child" will each have their own primary account. iCloud now appears to store two version - the "primary" version and the "secondary" version. Both are updatable. So: What "Dad" does in "Dad's Account" will sync with all Dad's devices (where he is logged in a primary) but not to Mum's or Childs. However: if Mum or Child update their version of Dad - it will still synchronise between them and all their devices... but Dad won't see it!!

Bad apple!