Apart from my primary iCloud account, I have a secondary account for content I share with my wife.
Unfortunately, my Notes on that account are not converted to the new iOS 9 Notes format.
How can I upgrade / convert these notes to iOS 9?
This secondary iCloud account is only used on two iOS 9 devices.
iPhone 6, iOS 8.1.2
I don't believe you can use the new notes format unless they are used in conjunction with a primary account.
I don't believe you can use the new notes format unless they are used in conjunction with a primary account.
See the following: Upgrade your notes with iOS 9 and OS X El Capitan - Apple Support
"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."
😢
I believe I already said that.
How can I convert Notes to iOS 9?
