Contacts do not sync between iphone and imac

I've tried all the suggestions I could find here, to reset icloud, contacts, etc.

For whatever reason when I add a new contact in my iphone, it never gets updated on my iMac and vice versa.

I've restarted both devices, opened iTunes on my iMac and hit "sync" to my iphone and nothing really happened.

I turned "contacts" off and then on again on my iMac and on my iPhone and did not fix this either. Some of my new contacts on my iphone just appear as phone numbers with no contact details on my iMac.

Any ideas how to fix this?