iCloud / iOS / Mac Syncing Troubles I have an iPhone 7 running iOS 12.1.4, and a MacBook Pro running OS 10.13.6. I am running iCloud using the same ID, syncing contacts from both devices. This should sync seamlessly, but it doesn't. I have duplicates on the Mac, and the iPhone; contacts that appear on the Mac, and not the iPhone; and contacts that appear on the iPhone, and not the Mac. I want to merge the two databases into iCloud, and eliminate duplicates. I have tried logging out of iCloud on both devices, waiting 30 minutes, and re-connecting. I still have the same issue. Any suggestions as to how I can get my contacts in sync in all three locations would be greatly appreciated.
To remove duplicate contacts:


  
  Make a copy of your contacts.
  Open Contacts.
  From the Card menu, select Card > Look for Duplicates.
  When asked, click Merge.
  Repeat steps 2 and 3 until no duplicates are found.
  Make another copy of your iCloud Contacts.
  



https://support.apple.com/en-us/HT203565


Then sync those contacts to iCloud. 

Afterwards, turn off contacts on the iPhone in iCloud settings, 
remove all remaining contacts and turn it on again.