** Opus Domini uses iCloud to share information across the different versions and devices. So in order to sync information between your different devices you will be needing to use a compatible combination of OS X and iOS. Otherwise your Mac will be storing information in one place and your iPad/iPhone will be storing the information in another, breaking the sync.
Compatible combinations are:
Macs running Mavericks will sync with iPads/iPhones running iOS 7
Macs running Yosemite will sync with iPads/iPhones running iOS 8