contacts don't sync

Hi

I have a problem syncing Contacts from my MacBook Pro Retina running Mac OS 10.9.5 to my iPhone 5s with iOS 8.3. I have somehow managed to sync all contacts. But now when I add a single contact on the Book, it is not synced to the phone. (Syncing via USB cable.) Will it sync properly if I upgrade the Book from 10.9.5 to Yosemite? Well why don't I just try? I'm not sure which things will NOT work any longer after that. Never change a winning team!

Thank you for your help - Hening.