Contacts not synching between MacPro, laptop and iPad

When my client adds a contact card to his Contacts on his Mac Pro, it doesn't sync to his laptop or iPad. What would cause this, and how can the problem be fixed? Also, how do you back up the Address Book in Yosemite?

I don't know the best community to post this to, please move it if there's a better one. Thanks.

Mac Pro 5,1 (Mid 2012), 32GB RAM, Yosemite 10.10.3

MacBook Pro 9,1 (Mid 2012), 8GB RAM, Yosemite 10.10.3

iPad (4th Generation, October 2012, Wi-Fi + Cellular MM), (32 GB, 4.2 GB available)

John H.

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