New notes created in iCloud or on iOS10 will only sync to Macs running El Capitan or higher. They will no longer sync to systems running OSX Yosemite or earlier.
Despite that, some syncing is still happening in iCloud because notes created on one Yosemite Mac will sync with the Notes App on another other Yosemite Mac. BUT these notes will not show up in iCloud or on your wonderful new iOS10 Phone.
Conversely, notes will sync across iCloud, iOS10 devices and Macs running El Capitan but those notes will not appear on a Mac running Yosemite or earlier.
Part of the reason for this may be that in iCloud Mail the ‘Notes’ Folder is no longer visible.
For anyone running two or more Macs that straddle the age gap between Yosemite and El Capitan, I would advise using a free Gmail account to sync Notes and say goodbye to the bag of hurt that is iCloud.
If you have a Mac that is running Yosemite but is too old to install Sierra – and missed the boat in purchasing El Capitan which has now been displaced by Sierra – call Apple and complain. They can provide a link to download previous systems that are no longer available in the App Store or your Previous purchases.
Dear Apple, was Notes Sharing so fucking vitally important that you would screw up things for anyone running systems older than Yosemite? Oh and thanks for removing PPTP VPN – the only one that works with BT’s crappy Fibre broadband. And why can’t I turn off those annoying new keypad noises – I was happy with a clicking sound. I swear to god my iPhone pauses sometimes to load up the spacebar donk!